Tunnel location in transparent 3-dimensional CT in anatomic double-bundle anterior cruciate ligament reconstruction with the trans-tibial tunnel technique

Development of an Original Three-Dimensional Computed Tomography Scan Method and Imaging Process for Surgical Support of the Anterior Cruciate Ligament

Three-dimensional computed tomography (3D CT) scan images are useful as they can provide information essential for surgical support, particularly in orthopedic surgery. In the case of anterior cruciate ligament (ACL) reconstruction, a 3D CT scan is important in preoperative simulation. Furthermore, it is associated with a reduced risk of revision surgery because the angle of the foramen magnum changes with the femoral muscle mass. However, the CT scan system geometry has several limitations. For example, the patient's posture is limited during the procedure. Herein, we report an original CT scan method and 3D imaging process for surgical support of the ACL.

Accuracy of Femoral Tunnel Localization With Mixed Reality Technology-Assisted Single-Bundle ACL Reconstruction

Background

It is clinically challenging to accurately drill femoral and tibial tunnels to reconstruct the anterior cruciate ligament (ACL). Mixed reality (MR) technology, a further development of virtual reality technology, presents virtual scene information in real time and establishes an interactive feedback information loop among the real world, the virtual world, and the user.

Purpose/Hypothesis

The purpose of this study was to investigate the structural and early clinical outcomes of ACL reconstruction assisted by MR technology. It was hypothesized that MR technology would improve the accuracy of tunnel localization.

Study Design

Cohort study; Level of evidence, 3.

Methods

Included were 44 patients at a single institution who underwent arthroscopic single-bundle ACL reconstruction between June 2020 and March 2022. Reconstruction with the aid of MR technology was performed in 21 patients (MR group), and conventional arthroscopic reconstruction was performed in 23 patients. Postoperatively, the parameters related to the bone tunnel positioning were compared by computed tomography imaging with 3-dimensional (3D) reconstruction, and 12-month postoperative clinical outcomes were assessed with the Lysholm and International Knee Documentation Committee scores.

Results

There was no statistically significant difference in projection angles in the coronal, axial, or sagittal plane between the preoperative virtually created tunnel guide pin and the actual tunnel (P > .05 for all). In the MR group, the center of the femoral tunnel exit was closer to the apex of the lateral femoral condyle along the proximal-distal axis (14.07 ± 4.12 vs 17.49 ± 6.24 mm for the conventional group; P < .05) and the graft bending angle was lower (117.71° ± 8.08° vs 127.81° ± 11.91° for the conventional group; P < .05). The scatterplot of the femoral tunnel location distribution showed that the entrance and exit points in the MR group were more concentrated and closer to the ideal location of the preoperative design than in the conventional group. Patients in both groups had significant preoperative-to-postoperative improvement based on outcome scores (P < .001 for all), with no significant difference between groups.

Conclusion

ACL reconstruction with the aid of MR technology allowed for more accurate positioning and orientation of the femoral tunnel during surgery when compared with conventional reconstruction.

Evaluation of a novel lower radiation computed tomography protocol for assessment of tunnel position post anterior cruciate ligament reconstruction

Background

Anterior cruciate ligament (ACL) reconstruction is a common orthopaedic procedure. We developed a novel, low dose computed tomography (LDCT) protocol to assess tunnel position post-operatively. The effective radiation dose of this protocol is < 0.5millisieverts (mSv), which is significantly less than the 2 mSv dose for a conventional CT protocol. The aim of this study was to assess the accuracy of the LDCT protocol for determining tunnel position.

Methods

Twenty-six patients who underwent primary ACL reconstruction were included in the study. A LDCT scan was performed 6 weeks post-operatively. Femoral and tibial tunnel positions were measured on three dimensional (3D) reconstructions using previously validated techniques. Measurements were performed independently by three observers at two time points, 4 weeks apart.

Results

There was excellent intra- and inter-rater reliability for all measurements using the images obtained from the LDCT protocol. Intra-class correlation coefficient (ICC) values were > 0.9 for all measurements.

Conclusions

The LDCT protocol described in this study accurately demonstrates femoral and tibial tunnels post ACL reconstruction, while exposing the patient to a quarter of the radiation dose of a conventional CT. This protocol could be used by orthopaedic surgeons for routine post-operative imaging, in place of plain film radiographs.

Inclination of Blumensaat's line influences on the accuracy of the quadrant method in evaluation for anterior cruciate ligament reconstruction

PURPOSE

The quadrant method is used to evaluate the bone tunnel position with the grid based on the Blumensaat's line in anterior cruciate ligament (ACL) reconstruction. This study aimed to clarify the influence of variation in the Blumensaat's line on the accuracy of the quadrant method measurements.

METHODS

A retrospective review of the radiological records of patients aged 18-30 years who underwent computed tomography (CT) scanning of the knee joint was conducted. The Blumensaat's line inclination angle (BIA), along with the most posterior point of the posterior condyle (point P) position using the quadrant method and morphology of the Blumensaat's line were measured on true lateral transparent three-dimensional CT images of the distal femoral condyle in 147 patients. Statistical analysis was conducted to determine associations among these measurements.

RESULTS

BIA was 37.5° (standard deviation 4.2°; range 27°-48°). The point P position was significantly correlated with BIA in the high/low (R² = 0.590, P < 0.0001) and deep/shallow (R² = 0.461, P < 0.0001) directions. The morphology of the Blumensaat's line was straight in 35 knees (23.8%); whereas, the remaining 112 knees (76.2%) were not straight but had some hill on the Blumensaat's line. No significant difference among the morphological variation of the Blumensaat's line was observed in BIA and the point P position.

CONCLUSION

There was a strong correlation between BIA and the point P measured using the quadrant method, suggesting the influence of the Blumensaat's line on the accuracy of the quadrant method measurements in ACL reconstruction. As for the clinical relevance, surgeons should be careful in application of the quadrant method for ACL reconstruction, because the variation of the Blumensaat's line inclination influences the accuracy of this method.

Anatomic femoral tunnel placement is difficult by the transtibial technique: comparison of three different femoral tunnel drilling techniques in double-bundle anterior cruciate ligament reconstructions

PURPOSE

To compare the position and direction of femoral and tibial tunnels for both the anteromedial bundle (AMB) and posterolateral bundle (PLB) among three different femoral tunnel drilling techniques, transtibial (TT), transportal (TP), and outside-in (OI) techniques, in anatomic double-bundle ACL reconstruction to clarify advantages and disadvantages of each technique.

METHODS

One-hundred and thirty-nine patients underwent primary ACL reconstruction with an autologous semitendinosus tendon in our institution between 2014 and 2016. Thirteen patients were excluded according to the exclusion criteria. Of the 126 patients, 98 patients agreed to be included in this study. Patients were then randomized into three groups according to the femoral tunnel drilling technique; the TT, TP, and OI groups. Femoral and tibial tunnel angles and positions were measured using three-dimensional computed tomography.

RESULTS

Of patients who agreed to be included in this study, eight patients (seven in TT and one in OI) were excluded since the femoral tunnel could not be created at the intended position. Eighty-six patients (29 in TT, 29 in TP, and 28 in OI) were included for the analyses. Tunnel angles, as well as tunnel lengths, had significant differences among different techniques depending on each technique's characteristics. In terms of tunnel position, femoral tunnel positions of both the AMB and PLB in the TT group were significantly higher than those in the TP group (AMB: p = 0.003, PLB: p = 0.001), and the PLB tunnel position in the TP group had significantly smaller vaciance than that in the TT group (p = 0.004) and OI group (0.002).

CONCLUSIONS

The femoral tunnel positions created by the TT technique were significantly higher, with larger variance, than the TP technique in double-bundle ACL reconstruction, although the positions seemed to be within anatomical footprint. In addition, there were several cases in which femoral tunnels could not be created at the intended position by the TT technique.

LEVEL OF EVIDENCE

I.

Do Rotation and Measurement Methods Affect Reliability of Anterior Cruciate Ligament Tunnel Position on 3D Reconstructed Computed Tomography?

Background:

The literature has seldom investigated the anterior cruciate ligament (ACL) tunnel position while considering the effect of rotation of 3-dimensional computed tomography (3D-CT) images during measurements.

Hypothesis:

We hypothesized that (1) measurement of the ACL tunnel position in the femur and tibia through use of 3D-CT is considerably influenced by rotation of the 3D model and (2) there exists a reliable measurement method for ACL tunnel position least affected by rotation.

Study Design:

Controlled laboratory study.

Methods:

The 3D-CT images of 30 randomly selected patients who underwent single-bundle ACL reconstruction were retrospectively reviewed. For femoral tunnel assessments, rectangular reference frames were used that involved the highest point of the intercondylar notch and outer margins of the lateral femoral condyle (method 1), the highest point of the intercondylar notch and outer margins of the lateral wall of the intercondylar notch (method 2), and the lowest point of the intercondylar notch and outer margins of the lateral femoral condyle (method 3). For tibial tunnel assessments, rectangular reference frames with the cortical outline at the articular surface of the tibia (method A) and the cortical outline of the proximal tibia (method B) were used. For both femoral and tibial assessments, the tunnel positions at 5°, 10°, and 15° of rotation of the 3D model were compared with that at a neutral position.

Results:

The values measured by methods 1 and 3 showed significant differences at greater than 5° of rotation compared with the value at the neutral position, whereas method 2 showed relatively consistent results. However, the values measured with both methods A and B showed significant differences at greater than 5° of rotation compared with the value at the neutral position.

Conclusion:

The tunnel position on 3D-CT images was significantly influenced by rotation during measurements. For femoral tunnel position, measurement with a reference frame using the lateral wall of the intercondylar notch (method 2) was the least affected by rotation, with relatively consistent results.

Clinical Relevance:

This study demonstrates that measurement using the lateral wall of the intercondylar notch might be a consistent and reliable method for evaluating the ACL femoral tunnel position considering the effect of 3D-CT image rotation during measurements. However, both methods to measure tibial tunnel position described in this study were similarly affected by rotation.

Comparison of three approaches for femoral tunnel during double-bundle anterior cruciate ligament reconstruction: A case controlled study

BACKGROUND

It is still controversial whether which femoral tunnel creation technique is best during anterior cruciate ligament reconstruction (ACLR). We aimed to clarify the features of three different techniques based on the femoral tunnel position created with the same tunnel-creating concept and the measurement data.

METHODS

The femoral tunnel of double-bundle (DB) ACLR was created using the behind-remnant approach in a remnant preserved manner following the policy of our institute. The trans-tibial approach (TT) was applied for all primary ACL injured cases until December 2012. The trans-portal approach (TP) was applied from January to September 2013, and the outside-in approach (OI) was indicated from October 2013 to March 2014. We compared the femoral tunnel aperture positions with the postoperative three-dimensional computed tomography (3D-CT). Additionally, the femoral tunnel length and the septum distance of each anteromedial (AM) and posterolateral (PL) tunnel were analyzed.

RESULTS

The AM tunnel aperture position of TT was significantly higher and shallower than that of TP in knee flexion position. The femoral tunnel length of TP was significantly shorter than that of TT and OI. The septum between each tunnel of OI trended wider than that of TT and TP.

CONCLUSIONS

The AM tunnel aperture position of TT runs the risk of a high and shallow position. TP runs the risk of insufficiently short tunnel length. It is important to apply each method flexibly to each case because no single best approach was found.

Plain radiographs can be used for routine assessment of ACL reconstruction tunnel position with three-dimensional imaging reserved for research and revision surgery

PURPOSE

The position of the osseous tunnels and graft during anterior cruciate ligament (ACL) reconstruction has been the subject of multiple studies aiming for either anatomical placement or an alternative. The assessment of these positions, using post-operative imaging, is therefore of interest to the surgeon in both the evaluation of surgical performance and surveillance of potential complications. The purpose of this review is to identify the optimal use of imaging in both the surveillance of clinical practice and in planning revision surgery.

METHODS

A comprehensive systematic review was performed using Medline and Pubmed searches to identify radiological methods used to assess ACL reconstruction tunnel position. Commonly used methods were identified with correlation to either native anatomy or clinical results.

RESULTS

The findings suggest that plain radiographs can be used to assess tunnel position and identify grafts that are positioned non-anatomically and may be at increased risk of complications. Computer tomography (CT) offers additional information about the tunnel aperture shape and size that is of importance for revision surgery and research projects whilst magnetic resonance imaging (MRI) provides further assessment of both graft integrity and associated soft tissue damage.

CONCLUSION

In the surveillance of routine clinical practice, plain radiographs are sufficient to define tunnel position. The additional information provided by three-dimensional imaging is only required in revision surgery or research studies.

LEVEL OF EVIDENCE

IV.

Three-Dimensional CT Evaluation of Tunnel Positioning in ACL Reconstruction Using the Single Anteromedial Bundle Biological Augmentation (SAMBBA) Technique

BACKGROUND

Remnant preservation may confer important advantages in the anterior cruciate ligament (ACL)-reconstructed knee. However, the presence of a large remnant may obscure visualization and impair the ability to correctly place tunnels during surgery.

PURPOSE

To determine whether tunnel placement during anatomic ACL reconstruction using the single anteromedial bundle biological augmentation (SAMBBA) technique is consistent and precise when a large native remnant is preserved.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Included in this study were 99 patients undergoing an ACL reconstruction during which at least 50% of the native ACL was preserved. The femoral tunnel was created using an outside-in specific guide. The tibial tunnel was positioned in the anteromedial region of the ACL footprint, and the remnant was carefully preserved while drilling and passing the semitendinosus graft through it. Postoperatively, 3-dimensional computed tomography (3D CT) was used to evaluate tunnel placement. The mean tunnel locations were calculated and the standard deviation was used to evaluate precision of positioning. Inter- and intrareader agreement were determined to assess reliability of evaluation of tunnel position.

RESULTS

The center of the femoral tunnel was positioned at a mean 19.4% (SD, 2%) of the depth of the notch and a mean 23.1% (SD, 3.5%) of the lateral wall height. The center of the tibial tunnel was positioned at a mean 36.3% (SD, 3.8%) of the anteroposterior length of the tibial plateau and at a mean 47.0% (SD, 2.7%) of the mediolateral width. The small standard deviations demonstrate that this technique allows precise tunnel placement. The tunnel positions achieved were consistent with previous anatomic studies of femoral and tibial anteromedial bundle insertion. Intra- and interobserver reliability were high.

CONCLUSION

Three-dimensional CT evaluation demonstrated that despite the presence of a large remnant, placement of femoral and tibial tunnels for anatomic ACL reconstruction using the SAMBBA technique is consistent and precise.

Comparison of graft bending angle during knee motion after outside-in, trans-portal and trans-tibial anterior cruciate ligament reconstruction

PURPOSE

To determine graft bending angle (GBA) during knee motion after anatomic anterior cruciate ligament (ACL) reconstruction and to clarify whether surgical techniques affect GBA. Our hypotheses were that the graft bending angle would be highest at knee extension and the difference of surgical techniques would affect the bending steepness.

METHODS

Eight healthy volunteers with a mean age of 29.3 ± 3.0 years were recruited and 3D MRI knee models were created at three flexion angles (0°, 90° and 130°). Surgical simulation of the tunnel drilling was performed with anatomic tunnel position using each outside-in (OI), trans-portal (TP) and trans-tibial (TT) techniques on the identical cases. The models were matched to other knee positions and the GBA in 3D was measured using computational software. Double-bundle ACL reconstruction was analysed first, and single-bundle reconstruction was also analysed to evaluate its effect to reduce GBA. A repeated-measures ANOVA was used to compare GBA difference at three flexion angles, by three techniques or of three bundles.

RESULTS

GBA changed substantially with knee motion, and it was highest at full extension (p < 0.001) in each surgical technique. OI technique exhibited highest GBA for anteromedial bundle (94.3° ± 5.2°) at extension, followed by TP (83.1° ± 6.5°) and TT (70.0° ± 5.2°) techniques (p < 0.01). GBA for posterolateral bundle at extension were also high in OI (84.6° ± 7.4°), TP (83.0° ± 6.3°) and TT (77.2° ± 7.0°) techniques (n.s.). Single-bundle grafts did not decrease GBA compared with double-bundle grafts. In OI technique, a more proximal location of the femoral exit reduced GBA of each bundle at extension and 90° flexion.

CONCLUSION

A significant GBA change with knee motion and considerably steep bending at full extension, especially with OI and TP techniques, were simulated. Although single-bundle technique did not reduce GBA as seen in double-bundle technique, proximal location of femoral exits by OI technique, with tunnels kept in anatomic position, was effective in decreasing GBA at knee extension and flexion. For clinical relevance, high stress on graft and bone interface has been suggested by steep GBA at full extension after anatomic ACL reconstruction.

LEVEL OF EVIDENCE

Therapeutic study (prospective comparative study), Level II.

A systematic review of single- versus double-bundle ACL reconstruction using the anatomic anterior cruciate ligament reconstruction scoring checklist

PURPOSE

The aim of this systematic review was to apply the anatomic ACL reconstruction scoring checklist (AARSC) and to evaluate the degree to which clinical studies comparing single-bundle (SB) and double-bundle (DB) ACL reconstructions are anatomic.

METHODS

A systematic electronic search was performed using the databases PubMed (MEDLINE), EMBASE and Cochrane Library. Studies published from January 1995 to January 2014 comparing SB and DB ACL reconstructions with clinical outcome measurements were included. The items from the AARSC were recorded for both the SB and DB groups in each study.

RESULTS

Eight-thousand nine-hundred and ninety-four studies were analysed, 77 were included. Randomized clinical trials (29; 38%) and prospective comparative studies (29; 38%) were the most frequent study type. Most studies were published in 2011 (19; 25%). The most commonly reported items for both SB and DB groups were as follows: graft type (152; 99%), femoral and tibial fixation method (149; 97% respectively), knee flexion angle during graft tensioning (124; 8%) and placement of the tibial tunnel at the ACL insertion site (101; 66%). The highest level of documentation used for ACL tunnel position for both groups was often one dimensional, e.g. drawing, operative notes or o'clock reference. The DB reconstruction was in general more thoroughly reported. The means for the AARSC were 6.9 ± 2.8 for the SB group and 8.3 ± 2.8 for the DB group. Both means were below a proposed required minimum score of 10 for anatomic ACL reconstruction.

CONCLUSIONS

There was substantial underreporting of surgical data for both the SB and DB groups in clinical studies. This underreporting creates difficulties when analysing, comparing and pooling results of scientific studies on this subject.

Measurements of tunnel placements after anterior cruciate ligament reconstruction--A comparison between CT, radiographs and MRI

BACKGROUND

A non-anatomic placement of the femoral and tibial tunnels may affect outcome in anterior cruciate ligament (ACL) reconstructions. Tunnel placements are validated with varying imaging modalities. We compared measurements of tunnel placements between radiographs, computed tomography (CT) and magnetic resonance imaging (MRI) in a clinical setting, assessed the reliability and aimed to decide on a possible "gold standard".

METHODS

All patients who had undergone at least two of three modalities, radiographs, MRI and CT, after ACL reconstruction between January 2011 and June 2013 were included. Two radiologists measured tunnel placements according to a standardized protocol. Interobserver agreement was assessed with intraclass correlation coefficients (ICC), the intermodality differences with Bland-Atman plots. Radiation data for CT studies were collected.

RESULTS

Forty-six CTs, 45 radiographs and 30 MRIs were reviewed. Femoral inter-observer agreement for radiographs was ICC=0.64, for CT ICC=0.86 and for MRI ICC = 0.75. Tibial inter-observer agreement for radiographs was ICC=0.92, for CT-mip ICC=0.91, for CT and MRI ICC = 0.87. No intermodality differences between the femoral measurements were observed. In the tibia, there were differences between radiographs and CT (-3.9%), radiographs-MRI (-3.6%), CT-CT mip (3.2%) and CTmip-MRI (-3.1%). The effective radiation doses varied between 0.025 and 0.045 mSv, mean and median was 0.033 mSv.

CONCLUSION

There were differences in the tibial measurements between summation and single slice images. Only 3D-CT depicted the femoral tunnel in both directions. CT was consistently reliable in both femoral and tibial measurements. Effective radiation dose from CT was lower than previously reported. CT can safely be used in routine clinical practice to evaluate tunnel placements after ACL reconstruction.

A new behind-remnant approach for remnant-preserving double-bundle anterior cruciate ligament reconstruction compared with a standard approach

PURPOSE

To introduce a new behind-remnant approach for double-bundle (DB) anterior cruciate ligament (ACL) reconstruction and to compare the femoral tunnel positions of anteromedial (AM) and posterolateral (PL) bundles between the new and standard procedures by a three-dimensional computed tomography (3D-CT).

METHODS

During DB ACL reconstruction, two approaches for femoral tunnel creation were consecutively practiced from 2010 to 2012. The patients were evaluated retrospectively as a cohort study. A total of 200 primary ACL reconstructions have been performed using a transtibial approach. One approach was a standard approach from the front in which the ACL remnant was peeled off from the attachment, and two guide wires were inserted based on anatomic bony landmarks (standard group). The other approach was a new behind-remnant approach in which the ACL remnant was kept untouched and two guide wires were inserted at the posterior margin of the direct ACL insertion (behind-remnant group). The position of the AM and PL femoral tunnels was expressed on a 3D-CT reconstructive image using the quadrant method with a statistical analysis.

RESULTS

The depth of the AM center was 24 ± 6 % (mean and standard deviation) in the standard group and 22 ± 5 % in the behind-remnant group. The height of the AM tunnel center was 22 ± 8 % in the standard group and 31 ± 8 % in the behind-remnant group. The depth of the PL tunnel center was 32 ± 6 % in the standard group and 35 ± 5 % in the behind-remnant group. The height of the PL tunnel center was 47 ± 9 % in the standard group and 55 ± 7 % in the behind-remnant group. The AM and PL femoral tunnels in both groups were created within the normal anatomic footprint of the previous studies. The behind-remnant approach created a significantly lower femoral tunnel for both AM (p = 0.000) and PL tunnels (p = 0.000). The depth of both AM and PL tunnels was not significantly different between the two groups (n.s.).

CONCLUSION

The new behind-remnant procedure is technically simple and reproducible as a remnant-preserving ACL reconstruction.

LEVEL OF EVIDENCE

Cohort study, Level III.

Effects of Remnant Tissue Preservation on Clinical and Arthroscopic Results After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

BACKGROUND

Clinical utility of remnant tissue preservation after single-bundle anterior cruciate ligament (ACL) reconstruction has not been established. In addition, no studies have evaluated the clinical utility of remnant preservation after anatomic double-bundle ACL reconstruction.

HYPOTHESIS

The study hypotheses were as follows: (1) Subjective and functional clinical results may be comparable between anatomic double-bundle reconstructions that preserve the remnant tissue and those that resect the remnant tissue, (2) postoperative knee stability and the second-look arthroscopic evaluation may be significantly more favorable with the remnant-preserving reconstruction, and (3) the degree of the initial graft coverage may significantly affect postoperative knee stability.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 179 patients underwent anatomic double-bundle ACL reconstruction. Based on the Crain classification of ACL remnant tissue, 81 patients underwent the remnant-preserving procedure (group P) and the remaining 98 patients underwent the remnant-resecting procedure (group R). There were no differences between the 2 groups concerning all background factors, including preoperative knee instability and intraoperative tunnel positions. The patients were followed for 2 years or more.

RESULTS

The subjective and functional clinical results were comparable between the 2 reconstruction procedures. Side-to-side anterior laxity was significantly less (P = .0277) in group P (0.9 mm) than in group R (1.5 mm). The pivot-shift test was negative in 89% of group P and 78% of group R patients; the result for group R was significantly lower (P = .0460). In the arthroscopic observations, results for group P were significantly better than for group R concerning postoperative laceration and fibrous tissue coverage of the grafts (P = .0479).

CONCLUSION

Remnant preservation in anatomic double-bundle ACL reconstruction did not significantly improve subjective and functional results in the short-term evaluation, but it significantly improved postoperative knee stability. The degree of initial graft coverage significantly affected postoperative knee stability.

Evaluation of a behind-remnant approach for femoral tunnel creation in remnant-preserving double-bundle anterior cruciate ligament reconstruction - Comparison with a standard approach

PURPOSE

To evaluate a novel approach for femoral tunnel creation, a behind-remnant approach, in remnant-preserving double-bundle anterior cruciate ligament (ACL) reconstruction through comparison with a standard approach.

METHODS

Sixty patients who underwent remnant-preserving double-bundle ACL reconstruction were included. Thirty patients with a standard approach were classified as the standard group, and 30 patients with a behind-remnant approach as the behind-remnant (BR) group. The anteromedial bundle (AMB) and posterolateral bundle (PLB) were provisionally fixed at 20° and 45° of flexion to a graft tensioning system during surgery. Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. Femoral tunnel positions were then assessed using the quadrant method.

RESULTS

During flexion-extension, the BR group showed equivalent tension curves between AMB and PLB, while the standard group showed reciprocal tension curves. The tension on the PLB was lower than the AMB in response to anterior or rotatory loads in the BR group, while the AMB and PLB shared equivalent loads in the standard group. Tunnel position of the AMB in the BR group was lower and deeper, with smaller variances, than that in the standard group. Tunnel position of the PLB in the BR group was lower than that in the standard group.

CONCLUSIONS

In remnant-preserving double-bundle ACL reconstruction, a behind-remnant approach can be achieved without any removal of the remnant tissue, and could create a deeper and lower AMB tunnel and a lower PLB tunnel with higher reproducibility, showing equivalent tension curves between the AMB and PLB.

A modified quadrant method for describing the femoral tunnel aperture positions in ACL reconstruction using two-view plain radiographs

PURPOSE

A modified quadrant method was developed for description of femoral tunnel aperture positions on the sagittal plane after double-bundle anterior cruciate ligament (ACL) reconstruction, which can be measured by using two-view radiographs. The purpose of the study is to provide a new measurement method and to evaluate the reproducibility and accuracy of the method.

METHODS

Forty-one patients who had undergone a double-bundle ACL reconstruction were investigated. Two-view plain radiographs, a 45-degree-flexion posterior-anterior standing (Rosenberg) and a lateral view, were taken at 1 year postoperatively, and the femoral tunnel positions were measured. Intra- and inter-observer reproducibility was calculated by means of intra-class correlation coefficient (ICC). Also, the accuracy of the method was evaluated by comparing the measurement from three-dimensional computed tomography (3D-CT).

RESULTS

Intra-observer reproducibility was excellent (ICC > 0.9). Inter-observer reproducibility of antero-medial (AM) tunnel position was almost perfect (ICC > 0.8) and that of postero-lateral (PL) tunnel was substantial (ICC > 0.7). The accuracy of the method was assessed by comparing the measurement from 3D-CT and was found to be almost perfect (ICC > 0.8). With the modified quadrant method, the average height of AM and PL tunnels were 17.8 and 44.4 %, respectively, and the depth of AM and PL tunnels were 25.5 and 36.7 %, respectively.

CONCLUSIONS

A modified quadrant method was found to have acceptable reproducibility and accuracy. The method is useful for describing the femoral tunnel aperture positions in ACL reconstruction because of its easiness and simplicity. By using this method, it is possible to analyse the femoral tunnel position even in the cases without CT analysis.

LEVEL OF EVIDENCE

IV.

3D computer tomography for measurement of femoral position in acl reconstruction

Objective:

To validate intra- and inter-class correlation coefficients of a transparent 3D-TC protocol and investigate relationships between different axial rotations.

Methods:

Twenty unilateral knee TCs (iSite - Philips) were evaluated by means of a transparent 3D-TC OsiriX Imaging Software (v.3.9.4), 3D MPR protocol. Mathematical model of femoral tunnel projections acquired on vertical and horizontal rotations from -20 to +20 degrees. Height (h'/H) and length (t'/T) of tunnel projections have been analyzed by the Bernard and Hertel's method.

Statistics:

power of study=80%, ICC, ANOVA, p<0.05 (SPSS-19). Results: Transparent 3D-TC showed high reliability of both intra-observer (h'/H=0.941; t'/T=0.928, p<0.001) and inter-observer (h'/H=0.921; t'/T=0.890, p<0.001) ICC. ACL Length (t'/T) and Height (h'/H) projections were statistically different on vertical and horizontal rotations: p=0.01 and p<0.001, respectively.

Conclusion:

This new transparent 3D-TC protocol is an accurate and reproducible method that can be applied for ACL femoral tunnel or footprint measurement with high ICC reliability. Level of Evidence II, Descriptive Laboratory Study.

Effect of femoral tunnel position on graft tension curves and knee stability in anatomic double-bundle anterior cruciate ligament reconstruction

PURPOSE

To evaluate the effect of the femoral tunnel position of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) on the graft tension curves and knee stability in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty-five patients who underwent anatomic double-bundle ACL reconstruction were included. AMB and PLB were provisionally fixed to a graft tensioning system in the following settings during surgery: (1) AMB at 20° and PLB at 0° (A20P0), (2) AMB at 20° and PLB at 20° (A20P20), and (3) AMB at 20° and PLB at 45° (A20P45). Bundle tension was recorded during knee flexion-extension. A pivot shift test was also evaluated. Femoral tunnel positions of the AMB and PLB were then assessed by three-dimensional computed tomography, and the correlation between femoral tunnel position and tension change pattern or residual pivot shift was evaluated.

RESULTS

The depth of the PLB tunnel position was correlated with the extent of tension reduction in the PLB between 0° and 30° irrespective of graft fixation settings, while neither the AMB tunnel position nor the height of the PLB tunnel position affected the tension change pattern. Ten cases showed grade 1 pivot shift only in the A20P0 setting. The PLB tunnel position in the pivot shift-positive cases was significantly deeper than that in the pivot shift-negative cases (27.5 ± 6.2 and 34.1 ± 5.5%, respectively, P = 0.002).

CONCLUSIONS

In anatomic double-bundle reconstruction, deeper PLB tunnel position was correlated with the larger tension reduction in the PLB between 0° and 30°. Fixation of the AMB at 20° and the PLB at 0° resulted in residual pivot shift phenomenon in 10/45 cases, and the PLB tunnel position in the pivot shift-positive cases was significantly deeper than that in the pivot shift-negative cases. In anatomic double-bundle reconstruction, the placement of PLB femoral tunnel must not be too deep, as it might lead to significant tension reduction in the PLB near extension and thus insufficient tension in the PLB, resulting in residual pivot shift phenomenon.

LEVEL OF EVIDENCE

IV.

Graft-bending angle and femoral tunnel length after single-bundle anterior cruciate ligament reconstruction: comparison of the transtibial, anteromedial portal and outside-in techniques

We used immediate post-operative in vivo three-dimensional computed tomography to compare graft bending angles and femoral tunnel lengths in 155 patients who had undergone single-bundle reconstruction of the anterior cruciate ligament using the transtibial (n = 37), anteromedial portal (n = 72) and outside-in (n = 46) techniques. The bending angles in the sagittal and axial planes were significantly greater but the coronal-bending angle was significantly less in the transtibial group than in the anteromedial portal and outside-in groups (p < 0.001 each). The mean length of the femoral tunnel in all three planes was significantly greater in the transtibial group than the anteromedial portal and outside-in groups (p < 0.001 each), but all mean tunnel lengths in the three groups exceeded 30 mm. The only significant difference was the coronal graft- bending angle in the anteromedial portal and outside-in groups (23.5° vs 29.8°, p = 0.012). Compared with the transtibial technique, the anteromedial portal and outside-in techniques may reduce the graft-bending stress at the opening of the femoral tunnel. Despite the femoral tunnel length being shorter in the anteromedial portal and outside-in techniques than in the transtibial technique, a femoral tunnel length of more than 30 mm in the anteromedial portal and outside-in techniques may be sufficient for the graft to heal.

Transparent 3-dimensional CT in evaluation of femoral bone tunnel communication after ACL double-bundle reconstruction: comparison between outside-in and transportal technique

PURPOSE

The purpose of this study is to assess the incidence of post-operative femoral bone tunnel communication after anterior cruciate ligament double-bundle reconstruction (ACL-DBR) with two drilling techniques by transparent 3-dimensional computed tomography (CT) and elucidate the factors associated with post-operative femoral bone tunnel communication.

METHODS

Fifty-five patients underwent ACL-DBR using outside-in technique (Group A, 25 patients) and transportal technique (Group B, 30 patients) for the drilling of femoral tunnel. CT was taken at 1 week and 6 months post-operatively. The femoral and tibial bone tunnel orientation, position, the divergency and the distance of bone bridge between the tunnels were measured using reconstructed CT images. In order to identify the factors related to post-operative femoral bone tunnel communication, patients were divided into two groups depending on whether femoral bone tunnels communicated (Group F-C) or remained (Group F-R) at 6 months post-operatively.

RESULTS

Femoral bone tunnels in Group B were orientated horizontally and dorsally compared to those in Group A. Tunnel divergency between two femoral tunnels was greater in Group A (11.7°) than in Group B (10.0°). Average distance of bone bridge at 1 week post-operatively was 1.8 mm in Group A and 1.7 mm in Group B (n.s.). Post-operative femoral bone tunnel communication occurred in 16 patients (64 %) in Group A and in 18 patients (60 %) in Group B at 6 months after ACL-DBR, respectively (n.s.). Regarding tibial tunnels, there were no significant differences in tunnel orientation, position, divergency and incidence of post-operative tibial tunnel communication between Groups A and B. Mean distance of femoral bone bridge at 1 week in Group F-R (2.5 mm) was significantly greater than in Group F-C (1.3 mm) (p < 0.001).

CONCLUSIONS

There was no significant difference in the incidence of post-operative femoral tunnel communication between two techniques. To avoid post-operative femoral tunnel bone communication, more than 2 mm distance of bone bridge at surgery is recommended.

Simulated anterior cruciate ligament reconstruction using preoperative three-dimensional computed tomography

PURPOSE

The aim of this study was to ascertain the ideal far anteromedial portal location to avoid damaging the medial femoral condyle in anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty patients received preoperative computed tomography (CT) scans at 120° of knee flexion. Three-dimensional CT (3D CT) reconstruction of the knee was performed using volume rendering. The insertion of anteromedial (AM) and posterolateral bundle of ACL of the femur was marked on the 3D CT. A line (Line A) was drawn 8-mm proximal and parallel to the anterior ridge of the medial tibial plateau. A tangential line to the medial femoral condyle was drawn from the AM position that was already marked to Line A. The length from the intersection of the lines to the medial edge of the patellar tendon was measured.

RESULTS

In all 40 patients, the mean length between the medial edge of the patellar tendon and the far anteromedial portal was 27.5 ± 0.7 mm (range 19.8-34.5). In men 29.5 ± 0.7 mm (range 25-34.5); 28.7 ± 0.8 mm in the shorter group (height ≤ 170 cm) and 30.1 ± 1.2 mm in the taller group (height ≥ 170 cm). In women 25.5 ± 1.0 mm (range 19.8-30.5); 22.9 ± 1.0 mm in the shorter group (height ≤ 158 cm) and 29.6 ± 0.5 mm in the taller group (height ≥ 158 cm).

CONCLUSIONS

An optimum far anteromedial portal position was proposed. Knowing the optimum location of the far anteromedial portal position before surgery allows the surgeons to perform more safety ACL reconstruction.

LEVEL OF EVIDENCE

IV.

In vivo three-dimensional imaging analysis of femoral and tibial tunnel locations in single and double bundle anterior cruciate ligament reconstructions

BACKGROUND

Anatomic footprint restoration of anterior cruciate ligament (ACL) is recommended during reconstruction surgery. The purpose of this study was to compare and analyze the femoral and tibial tunnel positions of transtibial single bundle (SB) and transportal double bundle (DB) ACL reconstruction using three-dimensional computed tomography (3D-CT).

METHODS

In this study, 26 patients who underwent transtibial SB ACL reconstruction and 27 patients with transportal DB ACL reconstruction using hamstring autograft. 3D-CTs were taken within 1 week after the operation. The obtained digital images were then imported into the commercial package Geomagic Studio v10.0. The femoral tunnel positions were evaluated using the quadrant method. The mean, standard deviation, standard error, minimum, maximum, and 95% confidence interval values were determined for each measurement.

RESULTS

The femoral tunnel for the SB technique was located 35.07% ± 5.33% in depth and 16.62% ± 4.99% in height. The anteromedial (AM) and posterolateral (PL) tunnel of DB technique was located 30.48% ± 5.02% in depth, 17.12% ± 5.84% in height and 34.76% ± 5.87% in depth, 45.55% ± 6.88% in height, respectively. The tibial tunnel with the SB technique was located 45.43% ± 4.81% from the anterior margin and 47.62% ± 2.51% from the medial tibial articular margin. The AM and PL tunnel of the DB technique was located 33.76% ± 7.83% from the anterior margin, 45.56% ± 2.71% from the medial tibial articular margin and 53.19% ± 3.74% from the anterior margin, 46.00% ± 2.48% from the medial tibial articular margin, respectively. The tibial tunnel position with the transtibial SB technique was located between the AM and PL tunnel positions formed with the transportal DB technique.

CONCLUSIONS

Using the 3D-CT measuring method, the location of the tibia tunnel was between the AM and PL footprints, but the center of the femoral tunnel was at more shallow position from the AM bundle footprint when ACL reconstruction was performed by the transtibial SB technique.

Radiological evaluation for conflict of the femoral tunnel entrance area prior to anterior cruciate ligament revision surgery

PURPOSE

Anterior cruciate ligament (ACL) revision surgery is a demanding procedure and requires meticulous pre-operative clinical and radiological assessment. In clinical practice the position of the femoral tunnel is identified mainly using plain radiographs (XR). Two-dimensional computed tomography (2D-CT) and magnetic resonance imaging (MRI) are not yet routine imaging methods and are only performed in specific clinical indications or in the scientific setting. Several measurement methods describe the femoral tunnel after ACL reconstruction and indicate 'ideal or wrong' placement to the surgeon. The aim of this study is to provide a reliable measurement method to predict potential conflict between the pre-existing and the planned femoral tunnel entrance area (FTEA).

METHODS

Ten patients with primary ACL reconstruction served as a reference group to describe our desired FTEA. Their femoral tunnel positioning was measured on XR and 2D-CT according to published measurement methods. These results were compared to the FTEA measured with a new technique on 3-dimensionally reconstructed CT-images (3D-CT) based on intra-operative landmarks. Twenty patients requiring ACL revision surgery underwent identical radiological examination. The mean values of the reference group were compared to each measurement of the patients requiring revision surgery.

RESULTS

3D-CT measurements found potential conflicts in nine out of 20 patients, which all proved to be true during arthroscopic revision surgery. Only one of these patients was identified in all XR and 2D-CT measurements. In 12 out of all 30 patients some measurements on XR or 2D-CT could not be recorded.

CONCLUSION

3D-CT reconstruction shows the most accuracy in depicting conflict of the pre-existing and desired femoral tunnel prior to ACL revision surgery. The desired FTEA must be defined for each surgeon and his individual technique. In contrast, precision of conventional measurement techniques on XR and 2D-CT is low and does not qualify for this purpose.

Restoration of sagittal and transverse plane proprioception following anatomic double-bundle ACL reconstruction

PURPOSE

To investigate the restoration of knee proprioception after anatomic double-bundle ACL reconstruction.

METHODS

Eleven subjects who underwent anatomic double-bundle ACL reconstruction (12.5-15 months following surgery) and eleven healthy control subjects participated in the study. Sagittal and transverse plane threshold to detect passive motion (TTDPM) were assessed utilizing a customized isokinetic dynamometer by passively rotating the tibia about a fixed femur in both the sagittal plane and transverse plane at 0.25°/s until the subject signalled recognition of movement and movement direction. Based on the normality assumption, either dependent t test or Wilcoxon test was utilized to determine whether significant differences were present between the ACL-reconstructed and the uninjured contralateral limbs. Independent t test or Mann-Whitney test was utilized to compare between the ACL-reconstructed/uninjured contralateral and the external control limbs.

RESULTS

There were no significant differences in TTDPM measurement in eleven out of twelve comparisons between the ACL-reconstructed and the uninjured contralateral/external control limbs. The only statistical significant difference was found on TTDPM towards internal rotation direction from the externally rotated-test position between the ACL-reconstructed and the uninjured contralateral limbs (p = 0.01).

CONCLUSIONS

Based on a small sample of eleven subjects, the current results indicate a restoration of both sagittal and transverse plane TTDPM following the anatomic double-bundle ACL reconstruction.

LEVEL OF EVIDENCE

III.

Comparison of tunnel locations of double bundle ACL reconstruction using the conventional transtibial technique with anatomic tunnel locations using a 3D CT model

INTRODUCTION

The purposes of this study were: (1) to compare tunnel locations using the conventional transtibial technique with reference data, and (2) to identify factors that make it difficult to position the femoral tunnel correctly or contribute to breakage of the bone bridge between the two tibial tunnels.

MATERIALS AND METHODS

A prospective study was performed on 28 patients who underwent double bundle ACL reconstruction. Locations of each tunnel were determined using an anatomic coordinate axes method (ACAM). Measurements included: thickness of the bone bridge between tibial two tunnels (BB), height from the union (HU) point to expected joint surface, the ratio between the length of Blumensaat's line and the anterior-posterior length of the lateral femoral condyle (RBL), and the ratio between anterior-posterior and proximal-distal lengths of the medial wall of the lateral femoral condyle (RAPPD).

RESULTS

The posterior-anterior direction of femoral AM tunnel, the proximal-distal direction of femoral PL tunnel, and the posterior-anterior direction of femoral PL tunnel were statistically significantly different from the reference data. In correlation analyses between BB or HU and other variables, the AM tibial tunnel and RBL showed a moderate negative correlation. The cutoff point for tunnel breakage was an RLB of 1.14, meaning that the possibility of bone bridge breakage would increases for RBL values of >1.14.

CONCLUSIONS

It seems that conventional transtibial drilling technique used during double bundle ACL reconstruction does not reproduce correct tunnel locations compared with reference data. This problem was found to be related to the bony geometry of the medial wall of the lateral femoral condyle or the bone bridge between the two tibial tunnels. Our results indicate that RBL should be determined by pre-operative CT or plain lateral radiography, and that transtibial single bundle reconstruction or double bundle reconstruction using other methods should be attempted when the RBL exceeds 1.14.

A quantitative technique to create a femoral tunnel at the averaged center of the anteromedial bundle attachment in anatomic double-bundle anterior cruciate ligament reconstruction

Background

In the anatomic double-bundle ACL reconstruction, 2 femoral tunnel positions are particularly critical to obtain better clinical results. Recently, a few studies have reported quantitative identification methods for posterolateral (PL) bundle reconstruction. Concerning anteromedial (AM) bundle reconstruction, however, no quantitative clinically available methods to insert a guide wire at the center of the direct attachment of the AM mid-substance fibers have been reported to date.

Methods

First, we determined the center of the femoral attachment of the AM mid-substance fibers using 38 fresh frozen cadaveric knees. Based on this anatomical sub-study, we developed a quantitative clinical technique to insert a guide wire at the averaged center for anatomic double-bundle ACL reconstruction. In the second clinical sub-study with 63 patients who underwent anatomic ACL reconstruction with this quantitative technique, we determined the center of an actually created AM tunnel. Then, we compared the results of the second sub-study with those of the first sub-study to validate the accuracy of the quantitative technique. In both the sub-studies, we determined the center of the anatomical attachment and the tunnel outlet using the “3-dimensional clock” system. The tunnel outlet was evaluated using the “transparent” 3-dimensional computed tomography.

Results

The averaged center of the direct attachment of the AM bundle midsubstance fibers was located on the cylindrical surface of the femoral intercondylar notch at “10:37” (or “1:23”) o’clock orientation in the distal view and at 5.0-mm from the proximal outlet of the intercondylar notch (POIN) in the lateral view. The AM tunnel actually created in ACL reconstruction was located at “10:41” (or “1:19”) o’clock orientation in the average and at 5.0-mm from the POIN. There was no significant difference between the 2 center locations.

Conclusions

The quantitative technique enabled us to easily create the femoral AM tunnel at the averaged center of the direct attachment of the AM bundle midsubstance fibers with high accuracy. This study reported information on the geometric location of the femoral attachment of the AM bundle and a clinically useful technique for its anatomical reconstruction.

Single photon emission computerized tomography and conventional computerized tomography (SPECT/CT) for evaluation of patients after anterior cruciate ligament reconstruction: a novel standardized algorithm combining mechanical and metabolic information

PURPOSE

The purpose of this study was to introduce a novel standardized algorithm using SPECT/CT, which promises the potential combined assessment of the biology of the joint in particular the bone-graft-fixation complex and the 3D tunnel placement in patients after ACL reconstruction. Its clinical application and inter- and intra-observer reliability should be critically evaluated.

METHODS

A novel SPECT/CT localization scheme consisting of 13 tibial, 9 femoral and 4 patellar regions on standardized axial, coronal and sagittal slices is proposed. The tracer activity on SPECT/CT was localized and recorded in 25 consecutive patients using a 3D volumetric and quantitative analysis software. The inter- and intra-observer reliability was assessed for localization and tracer activity. The tunnel position was assessed in 3D-CT using standardized frames of reference. The inter- and intra-observer reliability (OR) of the measured distances were calculated (ICC).

RESULTS

The localization scheme for tracer uptake analysis was useful and easily applicable in all 25 knees. It showed very high inter-OR and intra-ORs for all regions (ICC > 0.80). Tibial and femoral tunnel position measurements showed strong agreement between the readings of the two observers; the ICCs for the position, angulation, length and entry point of the femoral tunnel were >0.88 (intra-OR) and >0.86 (inter-OR). The ICC for the position of the tibial tunnel (angulation, length and entry point) was >0.79 (intra-OR) and >0.74 (inter-OR).

CONCLUSIONS

The SPECT/CT algorithm presented is highly reliable and clinically feasible. Combining the 3D-mechanical information on tunnel placement and attachment areas and the 3D metabolic data will be helpful in evaluating patients with pain after ACL reconstruction.

Comparison of tunnel orientation between transtibial and anteromedial portal techniques for anatomic double-bundle anterior cruciate ligament reconstruction using 3-dimensional computed tomography

PURPOSE

The aim of this study was to compare femoral and tibial tunnel placement, angle, and length between transtibial and anteromedial portal techniques for anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

Fifty patients were randomized to the 2 groups, and a femoral tunnel was created through the tibial tunnel (transtibial) and the far anteromedial portal (AMP) in 25 patients each. Both groups underwent anatomic double-bundle ACL reconstruction with hamstring tendons. Volume-rendering computed tomography (CT) was used to evaluate femoral and tibial tunnel placement, and transparent 3-dimensional CT image reconstruction, to evaluate tunnel angles, on the seventh postoperative day. Femoral tunnel length was measured intraoperatively.

RESULTS

Anteromedial bundle (AMB) and posterolateral bundle (PLB) femoral tunnels were placed significantly lower and deeper with the AMP technique (shallow/deep direction: 21% and 30%, high/low direction: 18% and 48%) than with the transtibial technique (25% and 34%, 12% and 43%). Except for the tibial tunnel angle in the axial plane, AMB and PLB femoral and tibial tunnel angles differed significantly in 3 dimensions. AMB and PLB femoral tunnel lengths were significantly shorter with the AMP technique (AMB: 33 mm, PLB: 32 mm) than with the transtibial technique (AMB: 49 mm, PLB: 37 mm) (P < .001 and P = .001). Both femoral tunnel lengths in the AMP group correlated significantly with the tunnel angle in the sagittal (AMB: r = 0.69, PLB: r = 0.51) and axial (AMB: r = 0.58, PLB: r = 0.75) planes.

CONCLUSIONS

AMB and PLB femoral tunnels were placed significantly deeper, lower, and closer to the femoral footprint reported in previous cadaveric studies in the anteromedial portal technique than in the transtibial technique. Femoral tunnel length was significantly shorter in the anteromedial portal group than in the transtibial group.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Comparative analysis of femoral tunnels between outside-in and transtibial double-bundle anterior cruciate ligament reconstruction: a 3-dimensional computed tomography study

PURPOSE

The objectives of this study were (1) to compare locations of the femoral tunnels created by outside-in and transtibial techniques and the reference data and (2) to compare the diameter of the tunnel entrance based on the real reaming size.

METHODS

A comparative study was performed with 20 outside-in and 22 transtibial double-bundle anterior cruciate ligament reconstruction patients. Computed tomography scans of the operated knees of the outside-in and transtibial groups were performed at 1.25 days (range, 1 to 3 days) and 2.7 weeks (range, 3 days to 4 weeks), respectively. Three-dimensional surface models were then produced. For all 3 plane data sets, the positions of the femoral tunnels were measured by an anatomic coordinate axis method. For comparison of the tunnel diameter at the entrance of tunnel, the difference between the real reaming and measured diameter was determined first on computed tomography images. Subsequently, the differences in the outside-in and transtibial techniques were compared.

RESULTS

In the comparison between outside-in and reference data, the posterior-anterior direction of the posterolateral (PL) tunnel showed an anterior position compared with reference data, even though it was positioned more posteriorly compared with that of the transtibial technique (P = .003). In the comparison between transtibial and reference data, the posterior-anterior direction of the anteromedial (AM) and PL tunnels showed an anterior position compared with reference data (P = .019 and P = .005, respectively). The transtibial technique showed significantly larger diameters in both AM and PL tunnels (P < .001 and P < .001, respectively).

CONCLUSIONS

The outside-in technique showed more accurate replication of the femoral tunnels than the transtibial technique, particularly the AM tunnel of the femur. The transtibial technique showed an ellipsoidal tunnel configuration at the entrance of the tunnel, which suggests that eccentric reaming is unavoidable because the reaming angle is determined by the tibial tunnel.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

A CT-based classification of prior ACL femoral tunnel location for planning revision ACL surgery

PURPOSE

The purposes of this study are to describe an ACL femoral tunnel classification system for use in planning revision ACL reconstruction based on 3-D computed tomography (CT) reconstructions and to evaluate its inter- and intra-rater reliability.

METHODS

A femoral tunnel classification system was developed based on the location of the femoral tunnel relative to the lateral intercondylar ridge. The femoral tunnel was classified as Type I if it was located entirely below and posterior to the ridge as viewed from distally, Type II if it was slightly malpositioned (either vertically, anteriorly, or both), and Type III if it was significantly malpositioned. To evaluate the reproducibility of the classification system, CT scans of 27 knees were obtained from patients scheduled for revision ACL reconstruction, and 3-D reconstructions were created. Four views of the 3-D reconstruction of each femur were then obtained, and inter- and intra-observer reliability was determined following classification of the tunnels by eight observers.

RESULTS

Twenty-five tunnels were classified as Type I (5 tunnels), Type II (9 tunnels), or type III (11 tunnels) by at least 5 of 8 observers, while insufficient agreement was noted to classify two tunnels. The interobserver reliability of tunnel classification as type I, II, or III yielded a κ coefficient of 0.57, while intra-observer reliability yielded a κ coefficient of 0.67. Subclassification of type II femoral tunnels into the subgroups anterior, vertical, and both was possible in four of the nine type II patients. The interobserver reliability of the complete classification system yielded a κ coefficient of 0.50, while the intra-observer reliability yielded a κ coefficient of 0.54.

CONCLUSION

Classification of the location of ACL femoral tunnels utilizing 3-D reconstructions of CT data yields moderate to substantial inter- and intra-observer reliability.

LEVEL OF EVIDENCE

Diagnostic Level III.

Anatomic femoral tunnel drilling in anterior cruciate ligament reconstruction: use of an accessory medial portal versus traditional transtibial drilling

BACKGROUND

During anatomic anterior cruciate ligament (ACL) reconstruction, we have found that the femoral footprint can best be visualized from the anteromedial portal. Independent femoral tunnel drilling can then be performed through an accessory medial portal, medial and inferior to the standard anteromedial portal.

PURPOSE

To compare the accuracy of independent femoral tunnel placement relative to the ACL footprint using an accessory medial portal versus tunnel placement with a traditional transtibial technique.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten matched pairs of cadaveric knees were randomized such that within each pair, one knee underwent arthroscopic transtibial (TT) drilling, and the other underwent drilling through an accessory medial portal (AM). All knees underwent computed tomography (CT) both preoperatively and postoperatively with a technique optimized for ligament evaluation (80 keV with maximum mAs). Computed tomography was performed with a dual-energy scanner. Commercially available third-party software was used to fuse the preoperative and postoperative CT scans, allowing anatomic comparison of the ACL footprint to the drilled tunnel. The ACL footprint was marked in consensus by an orthopaedic surgeon and a musculoskeletal radiologist and then compared with the tunnel aperture after drilling. The percentage of tunnel aperture contained within the native footprint as well as the distance from the center of the tunnel aperture to the center of the footprint was measured.

RESULTS

The AM technique placed 97.7% ± 5% of the tunnel within the native femoral footprint, significantly more than 61.2% ± 24% for the TT technique (P = .001). The AM technique placed the center of the femoral tunnel 3.6 ± 1.2 mm from the center of the native footprint, significantly closer than 6.0 ± 1.9 mm for the TT technique (P = .003).

CONCLUSION

This study demonstrates that use of an accessory medial portal will facilitate more accurate placement of the femoral tunnel in the native ACL femoral footprint.

CLINICAL RELEVANCE

More accurate placement of the femoral tunnel in the native ACL femoral footprint should improve the ability to achieve more anatomic positioning of the ACL graft.

Rollback of the femoral condyle in anatomical double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to evaluate rollback of the femoral condyle in anatomical double-bundle anterior cruciate ligament reconstruction (ACL).

METHODS

Twenty-two subjects who underwent anatomical double-bundle ACL reconstruction were included in this study. More than 6 months after surgery, lateral radiographic imaging of the knee was performed with active full knee flexion. The most posterior tibiofemoral contact point was measured for evaluation of femoral rollback (rollback ratio). Flexion angle was also measured using the same radiograph, and the correlation between rollback and flexion angle was analyzed. As a control, radiographs of the healthy contralateral knees were evaluated. For clinical evaluation, side-to-side difference in anterior tibial translation (ATT) and pivot shift test were analyzed approximately 1 year after surgery.

RESULTS

The rollback ratios of the operated knees and the healthy contralateral knees were 28.7 ± 6.6 and 29.7 ± 6.7%, respectively, from the posterior edge of the tibia. No significant difference in rollback was observed. The flexion angles of the operated knees and the healthy contralateral knees were 136 ± 11° and 140 ± 9°, respectively. No significant difference in knee flexion angle was observed. Significant correlation between femoral rollback and knee flexion angle was observed. The side-to-side difference in ATT was 0.7 mm, and no cases of positive pivot shift were observed.

CONCLUSION

Anatomical double-bundle ACL reconstruction can restore normal femoral rollback in active full knee flexion. For clinical relevance, knees with anatomical double-bundle ACL reconstruction can flex with normal kinematics at the end of knee flexion angle.

LEVEL OF EVIDENCE

III.

A pilot study of anatomic double-bundle anterior cruciate ligament reconstruction with ligament remnant tissue preservation

PURPOSE

The purpose of this pilot study was to evaluate the preliminary results of an anatomic double-bundle anterior cruciate ligament (ACL) reconstruction procedure with ligament remnant tissue preservation.

METHODS

By use of the transtibial technique, 2 doubled semitendinosus tendons were grafted into 4 tunnels created at the center of each bundle attachment, penetrating the ACL remnant tissue. In total, 44 patients (27 male and 17 female patients) with an isolated ACL injury underwent ACL reconstruction with this procedure. The mean age of the patients was 29 years (range, 17 to 58 years). Postoperative clinical evaluations were performed at 16.6 months on average (range, 12 to 23 months). Radiologic evaluations were also performed to evaluate the tunnel location in the femur and the tibia.

RESULTS

The mean operation time was 86 minutes (range, 72 to 96 minutes) in the cases with ACL reconstruction only. Postoperatively, the mean anterior laxity was 0.7 mm. The postoperative pivot-shift test was negative in 81.8% of the patients, whereas there were no patients evaluated as ++. No patients showed any extension or flexion deficit. There were no patients evaluated as "nearly abnormal" or "abnormal" according to the International Knee Documentation Committee evaluation. The tunnel angles of the 4 tunnels were identical to those reported in a previous study.

CONCLUSIONS

The minimal 1-year clinical results of anatomic double-bundle ACL reconstruction with ligament remnant tissue preservation were comparable to previously reported results of anatomic double-bundle reconstruction without remnant tissue preservation.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Full knee extension magnetic resonance imaging for the evaluation of intercondylar roof impingement after anatomical double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to reveal the relationship between anatomically placed anterior cruciate ligament (ACL) graft and the intercondylar roof using magnetic resonance imaging (MRI).

METHODS

Twenty patients undergoing anatomical double-bundle ACL reconstruction were included in this study. Anatomical double-bundle ACL reconstruction was performed with two femoral tunnels (antero-medial; AM and postero-lateral; PL) and two tibial tunnels. Hamstring autograft was used in all cases. More than 6 months after operation, MRI was performed with full knee extension. The relationship between the graft and the intercondylar roof was evaluated using an axial view of the T2 image at the most distal slice of the intercondylar roof. Qualitative evaluation of the ACL graft was performed with a sagittal view of the T2 image. Tunnel placement was evaluated with three-dimensional computed tomography (3D-CT) and radiographs. The extension angle of the knee was also evaluated with 3D-CT.

RESULTS

In 12 subjects, the ACL graft touched the roof (Touch group) but no graft deformation was observed. In 8 subjects, no roof-graft contact was observed (Non-touch group). In 1 case, the ACL graft was bowed posteriorly. Signal intensity alteration of the graft was observed in 3 cases. No significant difference in femoral and tibial tunnel placement was observed between the Touch and Non-touch groups. All subjects attained full knee extension.

CONCLUSION

Although graft-roof impingement after anatomical double-bundle ACL reconstruction was suspected in some cases after the MRI evaluation, no extension loss in the knee was observed. In these suspected cases of impingement, long-term follow-up will be needed to determine the connection between any potential pathological effects. For the clinical relevance, MRI is an effective tool to determine the status of roof impingement in anatomical double-bundle ACL reconstruction.

Reliability of tunnel angle in ACL reconstruction: two-dimensional versus three-dimensional guide technique

PURPOSE

To compare the reliability of tibial tunnel position and angle produced with a standard ACL guide (two-dimensional guide) or Howell 65° Guide (three-dimensional guide) in the coronal and sagittal planes. In the sagittal plane, the dependent variables were the angle of the tibial tunnel relative to the tibial plateau and the position of the tibial tunnel with respect to the most posterior aspect of the tibia. In the coronal plane, the dependent variables were the angle of the tunnel with respect to the medial joint line of the tibia and the medial and lateral placement of the tibial tunnel relative to the most medial aspect of the tibia.

METHODS

The position and angle of the tibial tunnel in the coronal and sagittal planes were determined from anteroposterior and lateral radiographs, respectively, taken 2-6 months postoperatively. The two-dimensional and three-dimensional guide groups included 28 and 24 sets of radiographs, respectively. Tibial tunnel position was identified, and tunnel angle measurements were completed. Multiple investigators measured the position and angle of the tunnel 3 times, at least 7 days apart.

RESULTS

The angle of the tibial tunnel in the coronal plane using a two-dimensional guide (61.3 ± 4.8°) was more horizontal (P < 0.05) than tunnels drilled with a three-dimensional guide (64.7 ± 6.2°). The position of the tibial tunnel in the sagittal plane was more anterior (P < 0.05) in the two-dimensional (41.6 ± 2.5%) guide group compared to the three-dimensional guide group (43.3 ± 2.9%).

CONCLUSION

The Howell Tibial Guide allows for reliable placement of the tibial tunnel in the coronal plane at an angle of 65°. Tibial tunnels were within the anatomical footprint of the ACL with either technique. Future studies should investigate the effects of tibial tunnel angle on knee function and patient quality of life.

LEVEL OF EVIDENCE

Case-control retrospective comparative study, Level III.

Evaluation of the intercondylar roof impingement after anatomical double-bundle anterior cruciate ligament reconstruction using 3D-CT

PURPOSE

To reveal the relationship between anatomically placed anterior cruciate ligament (ACL) graft and the intercondylar roof using three-dimensional computed tomography (3D-CT).

METHODS

Twenty-four patients undergoing anatomical double-bundle ACL reconstruction were included in this study. Anatomical double-bundle ACL reconstruction was performed with two femoral tunnels (antero-medial; AM and postero-lateral; PL) and two tibial tunnels. Hamstring autograft was used in all cases. Six to eight weeks after operation and when the subjects had obtained full extension of the knee, 3D-CT was performed with full knee extension. In the 3D-CT, the ACL graft was also reconstructed and visualized three dimensionally. Tunnel placement was evaluated with 3D-CT and intra-operative radiographs. The extension angle of the knee was also evaluated with 3D-CT.

RESULTS

No intercondylar roof impingement was observed. In 12 subjects, the ACL graft touched the roof (Touch group) but no graft deformation was observed. In 12 subjects, no roof-graft contact was observed (Non-touch group). No significant difference in femoral and tibial tunnel placement was observed between the Touch and Non-touch groups. All subjects attained full knee extension.

CONCLUSION

We believe that 3D-CT is an effective means of evaluating impingement after ACL reconstruction. For the clinical relevance, when the grafts are positioned in an anatomical fashion, there is no risk of impingement, and surgeons can perform anatomical double-bundle ACL as an impingement-free reconstruction.

LEVEL OF EVIDENCE

III (Case control study).

Radiographic description of femoral tunnel placement expressed as intercondylar clock time in double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to propose an objective description of femoral tunnel position expressed as time of the intercondylar clock in ACL reconstruction using a simple radiograph for the sake of objective discussion and technical improvement. The reproducibility of the method was evaluated in double-bundle (DB) reconstructions.

METHODS

The first series of 54 knees in 54 patients who underwent primary "isometric" DB ACL reconstructions from 1995 to 2002 were randomly picked up. The second series of 48 knees in 48 patients with primary "anatomic" DB ACL reconstructions during 2007 were assessed as a recent femoral tunnel position with the same method. All DB reconstructions of ACL with the anteromedial (AM) and posterolateral (PL) bundles were performed with an arthroscopically assisted trans-tibial technique. The o'clock description of femoral tunnel placement was expressed using a weight-bearing posterior-anterior view at 45° of flexion (45° W/B PA view) of the knee. Assessment was undertaken with radiographs 1 year postoperatively.

RESULTS

The o'clock descriptions of femoral tunnel placement resulted in noon 40 min (standard deviation (SD): 10 min) for the AM bundle and one o'clock 40 min (SD: 20 min) for the PL bundle on average in the "isometric" reconstruction. In the "anatomic" reconstruction, the time descriptions of femoral tunnel placement were one o'clock 20 min (SD: 10 min) for the AM bundle and two o'clock 20 min (SD: 20 min) for the PL bundle on average. With the intra-examiner reproducibility assessment in the "anatomic" reconstruction, the differences between first and second assessments averaged 10 min (SD: 7 min) for femoral tunnel placement of the AM bundle and 12 min (SD: 9 min) of the PL bundle. Regarding the inter-examiner reproducibility, the differences between two examiners averaged 9 min (SD: 6 min) for femoral tunnel placement of the AM bundle and 14 min (SD: 9 min) of the PL bundle.

CONCLUSION

This simple radiographic assessment is reproducible and reliable for clinical use, and useful for the evaluation of ACL reconstructive procedures.

Anterior cruciate ligament tunnel position measurement reliability on 3-dimensional reconstructed computed tomography

PURPOSE

The purpose of this study was to evaluate intraobserver and interobserver reliability of anterior cruciate ligament tunnel location measurement by use of 3-dimensional reconstructed computed tomography (CT).

METHODS

Three-dimensional reconstructed CT images of 31 cadaveric knees were used in this study. Twenty-one knees were operated on with a double-bundle technique, and ten knees were operated on with a single-bundle technique. Femoral tunnel location was measured with 3 methods on the medial-lateral view of the lateral femoral condyle in the strictly lateral position. Tibial tunnel location was measured in the top view of the proximal tibia. The images were evaluated independently by 2 orthopaedic surgeons. A second measurement was performed, by both testers, after a 4-week interval.

RESULTS

The 3 methods of femoral tunnel location measurement had intraobserver intraclass correlation coefficients (ICCs) that ranged from 0.963 to 0.998 and interobserver ICCs that ranged from 0.993 to 0.999. Tibial tunnel measurement had intraobserver ICCs that varied between 0.957 and 0.998 and interobserver ICCs that varied between 0.993 and 0.996.

CONCLUSIONS

The measurement of the anterior cruciate ligament tunnel location on 3-dimensional reconstructed CT provided excellent intraobserver and interobserver reliability.

CLINICAL RELEVANCE

Three-dimensional reconstructed CT can be used for further studies to assess the effect of tunnel position on knee stability and patient outcomes.

Painful knee joint after ACL reconstruction using biodegradable interference screws- SPECT/CT a valuable diagnostic tool? A case report

With the presented case we strive to introduce combined single photon emission computerized tomography and conventional computer tomography (SPECT/CT) as new diagnostic imaging modality and illustrate the possible clinical value in patients after ACL reconstruction. We report the case of a painful knee due to a foreign body reaction and delayed degradation of the biodegradable interference screws after ACL reconstruction. The MRI showed an intact ACL graft, a possible tibial cyclops lesion and a patella infera. There was no increased fluid collection within the bone tunnels. The 99mTc-HDP-SPECT/CT clearly identified a highly increased tracer uptake around and within the tibial and femoral tunnels and the patellofemoral joint. On 3D-CT out of the SPECT/CT data the femoral graft attachment was shallow (50% along the Blumensaat's line) and high in the notch. At revision arthroscopy a diffuse hypertrophy of the synovium, scarring of the Hoffa fat pad and a cyclops lesion of the former ACL graft was found. The interference screws were partially degraded and under palpation and pressure a grey fluid-like substance drained into the joint. The interference screws and the ACL graft were removed and an arthrolysis performed.

In the case presented it was most likely a combination of improper graft placement, delayed degradation of the interference screws and unknown biological factors. The too shallow and high ACL graft placement might have led to roof impingement, chronic intraarticular inflammation and hence the delayed degradation of the screws.

SPECT/CT has facilitated the establishment of diagnosis, process of decision making and further treatment in patients with knee pain after ACL reconstruction. From the combination of structural (tunnel position in 3D-CT) and metabolic information (tracer uptake in SPECT/CT) the patient's cause of the pain was established.