Comparison of expected vs. actual tunnel position in anterior cruciate ligament reconstruction

Computer-assisted navigation in ACL reconstruction improves anatomic tunnel placement with similar clinical outcomes

BACKGROUND

While the use of navigation systems in anterior cruciate ligament (ACL) reconstruction theoretically improves tunnel placement accuracy and clinical outcomes, the existing literature remains inconclusive. We aimed to evaluate the potential benefits of navigated ACL reconstruction on tunnel placement and clinical outcomes.

METHODS

In this retrospective study, we evaluated a cohort of patients who underwent conventional or navigated (OrthoPilot system) primary ACL reconstruction at our institution from June 2004 to October 2009. Anteroposterior and lateral radiographic knee assessments were evaluated to assess postoperative tunnel positioning. Clinical outcomes, including the International Knee Documentation Committee classification, Lysholm score, and Tegner score, were evaluated preoperatively and 1-year postoperatively. Radiographic and clinical outcomes were compared and analysed using independent 2-sample t-tests and Chi-square tests.

RESULTS

Sixty patients met the inclusion criteria and were included for analysis, comprising of 26 navigated and 34 conventional reconstructions. Postoperative radiographs showed no differences in tibial tunnel position between both groups, but a significantly smaller deviation from the recommended position in the navigated group (navigated: 5.96 %; conventional: 7.92 %; p = 0.008). Femoral tunnel placements in the navigated group were significantly more perpendicularly away from the Blumensaat line (navigated: 38.90 %; conventional: 31.94 %; p = 0.001), with a greater deviation from recommended position (navigated: 11.00 %; conventional: 6.94 %; p = 0.009). There were no differences in 1-year postoperative clinical outcomes (p > 0.05).

CONCLUSION

Navigated ACL reconstruction resulted in a more anatomic femoral tunnel placement and similar clinical outcomes as conventional reconstruction. Further research should be conducted to clarify the potential biomechanical and clinical impacts of navigated ACL reconstruction.

The femoral tunnel view test during ACL reconstruction can ensure tunnel integrity

Objective

Violation of the posterior femoral cortex commonly referred to as posterior wall blowout, can be a devastating intraoperative complication in anterior cruciate ligament reconstruction (ACLR) and can lead to loss of graft fixation or early graft failure. This study describes and analyzes whether the femoral tunnel view test can ensure the integrity of the femoral tunnel during ACLR.

Methods

Intraoperative femoral tunnel integrity using the 360° arthroscopic view test was performed in 584 ACLR patients between 2014 and 2016. Posterior wall blowouts were described by their location along the femoral tunnel (i.e., near the aperture or more proximal) and by the depth of the tunnel blowout (<3 mm, 3–5 mm, >5 mm), corresponding to the length of the posterior cortical wall of the violated femoral tunnel. The time spent for the test was measured during ACLR. Complications related to the femoral tunnel view test were also evaluated.

Results

The femoral tunnel view test was performed in all 584 patients. In 12 patients (1%), the femoral tunnel presented a posterior cortical blowout that did not extend beyond 3 mm. Only four patients (0.6%) presented posterior wall blowout that extended beyond 5 mm. The time for the test was 40 s (±20 s). No complications related to the test were reported.

Conclusion

The femoral tunnel view test is effective for ensuring the integrity of the femoral tunnel during ACL reconstruction, without increasing the surgical time and without an increase in the complications rate.

Clinical relevance

The femoral tunnel view test is a quick and straightforward test able to provide an adequate view of the patient's anatomy to ensure tunnel integrity during ACLR.

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.

Radiologic assessment of femoral and tibial tunnel placement based on anatomic landmarks in arthroscopic single bundle anterior cruciate ligament reconstruction

BACKGROUND

Accurate tibial and femoral tunnel placement has a significant effect on outcomes after anterior cruciate ligament reconstruction (ACLR). Postoperative radiographs provide a reliable and valid way for the assessment of anatomical tunnel placement after ACLR. The aim of this study was to examine the radiographic location of tibial and femoral tunnels in patients who underwent arthroscopic ACLR using anatomic landmarks. Patients who underwent arthroscopic ACLR from January 2014 to March 2016 were included in this retrospective cohort study.

MATERIALS AND METHODS

45 patients who underwent arthroscopic ACLR, postoperative radiographs were studied. Femoral and tibial tunnel positions on sagittal and coronal radiographic views, graft impingement, and femoral roof angle were measured. Radiological parameters were summarized as mean ± standard deviation and proportions as applicable. Interobserver agreement was measured using intraclass correlation coefficient.

RESULTS

The position of the tibial tunnel was found to be at an average of 35.1% ± 7.4% posterior from the anterior edge of the tibia. The femoral tunnel was found at an average of 30% ± 1% anterior to the posterior femoral cortex along the Blumensaat's line. Radiographic impingement was found in 34% of the patients. The roof angle averaged 34.3° ± 4.3°. The position of the tibial tunnel was found at an average of 44.16% ± 3.98% from the medial edge of the tibial plateau. The coronal tibial tunnel angle averaged 67.5° ± 8.9°. The coronal angle of the femoral tunnel averaged 41.9° ± 8.5°.

CONCLUSIONS

The femoral and tibial tunnel placements correlated well with anatomic landmarks except for radiographic impingement which was present in 34% of the patients.

Is the clock face an accurate, precise, and reliable measuring tool for anterior cruciate ligament reconstruction?

PURPOSE

(1) To assess the use and practice of the clock face among surgeons who routinely perform anterior cruciate ligament (ACL) reconstructions, and (2) to assess the accuracy, precision, and reliability of 3 commonly used clock-face schemes in ACL reconstruction.

METHODS

First, 9 surgeons completed a questionnaire assessing the use and definition of the clock-face technique. Next, to assess the accuracy, precision, and reliability of the clock face, each surgeon estimated the "time" of 8 artificial femur models with a black dot located on the posterior aspect of the lateral condylar wall. The estimates were performed using 3 different clock-face schemes and were repeated 10 months later. Solutions for each specimen were obtained by use of a computer graphical interface.

RESULTS

More than half of the respondents (55%) use the clock face in ACL reconstructions, with the reported mean ideal "time" for a femoral tunnel in a right knee of 10:05 (SD, 31 minutes). When we accounted for the different clock definitions, this ideal position was found along the entire lateral condylar wall. In the assessment of the performance of the clock face, the mean error was 32 to 40 minutes (which translates to 3 to 4 mm) among the 3 clock schemes. The maximum error was 4 hours 0 minutes, and the range of responses was 1 hour 0 minutes to 4 hours 0 minutes depending on the specimen and clock scheme. Regardless of the clock scheme used, the intrarater and inter-rater reliabilities were similar-measuring, on average, 0.78 and 0.68, respectively.

CONCLUSIONS

The clock face continues to be commonly used in ACL reconstruction. Different clock-face definitions affect the position for the same "time." When the clock-face parameters were strictly defined, there was good reliability with borderline accuracy and poor precision.

CLINICAL RELEVANCE

Considering the borderline performance of the clock face in accuracy and poor precision, we recommend against using the clock face in ACL reconstruction.

Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction

BACKGROUND

Femoral tunnel positioning is a difficult, but important factor in successful anterior cruciate ligament (ACL) reconstruction. Computer navigation can improve the anatomical planning procedure besides the tunnel placement procedure.

METHODS

The accuracy of the computer-assisted femoral tunnel positioning method for anatomical double bundle ACL-reconstruction with a three-dimensional template was determined with respect to both aspects for AM and PL bundles in 12 cadaveric knees.

RESULTS

The accuracy of the total tunnel positioning procedure was 2.7 mm (AM) and 3.2 mm (PL). These values consisted of the accuracies for planning (AM:2.9 mm; PL:3.2 mm) and for placement (about 0.4 mm). The template showed a systematic bias for the PL-position.

CONCLUSIONS

The computer-assisted templating method showed high accuracy for tunnel placement and has promising capacity for application in anatomical tunnel planning. Improvement of the template will result in an accurate and robust navigation system for femoral tunnel positioning in ACL-reconstruction.

Radiographic findings in revision anterior cruciate ligament reconstructions from the Mars cohort

The Multicenter ACL (anterior cruciate ligament) Revision Study (MARS) group was developed to investigate revision ACL reconstruction outcomes. An important part of this is obtaining and reviewing radiographic studies. The goal for this radiographic analysis is to establish radiographic findings for a large revision ACL cohort to allow comparison with future studies. The study was designed as a cohort study. Various established radiographic parameters were measured by three readers. These included sagittal and coronal femoral and tibial tunnel position, joint space narrowing, and leg alignment. Inter- and intraobserver comparisons were performed. Femoral sagittal position demonstrated 42% were more than 40% anterior to the posterior cortex. On the sagittal tibia tunnel position, 49% demonstrated some impingement on full-extension lateral radiographs. Limb alignment averaged 43% medial to the medial edge of the tibial plateau. On the Rosenberg view (45-degree flexion view), the minimum joint space in the medial compartment averaged 106% of the opposite knee, but it ranged down to a minimum of 4.6%. Lateral compartment narrowing at its minimum on the Rosenberg view averaged 91.2% of the opposite knee, but it ranged down to a minimum of 0.0%. On the coronal view, verticality as measured by the angle from the center of the tibial tunnel aperture to the center of the femoral tunnel aperture measured 15.8 degree ± 6.9% from vertical. This study represents the radiographic findings in the largest revision ACL reconstruction series ever assembled. Findings were generally consistent with those previously demonstrated in the literature.

Computer-assisted surgery is not more accurate or precise than conventional arthroscopic ACL reconstruction: a prospective randomized clinical trial

BACKGROUND

Accurate and precise tunnel placement is critical to the success of anterior cruciate ligament (ACL) reconstruction. A new development, computer-assisted surgery, aids in placement of the ACL bone tunnels during surgery. Our hypothesis was that computer-assisted ACL reconstruction would allow more accurate and precise tunnel placement compared with conventional surgery.

METHODS

In a prospective, double-blind, randomized clinical study, 100 patients eligible for ACL reconstruction with a transtibial technique were stratified by surgeon and randomized to either conventional or computer-assisted surgery. Measurement of femoral and tibial tunnel placement with use of three-dimensional computed tomography (CT) was used as the primary outcome to compare conventional ACL surgery with computer-assisted surgery.

RESULTS

The placement of the femoral tunnel did not differ between groups (mean, 39.7% of the proximal-distal distance on the intracondylar axis [Blumensaat line] in the conventional group compared with 39.0% in the computer-assisted surgery group; p = 0.70). The anterior-posterior positioning of the tibial tunnel on the tibial plateau also did not differ significantly (38.9% in the conventional group compared with 38.2% in the computer-assisted surgery group; p = 0.58). There was no significant difference in the precision of either the femoral or the tibial tunnel placement between the two groups.

CONCLUSIONS

There was no significant difference in either the accuracy or the precision of tunnel placement between conventional and computer-assisted ACL reconstruction.

Tunnel position following posterior cruciate ligament reconstruction: an in vivo computed tomography analysis

The success of posterior cruciate ligament (PCL) reconstruction is dependent on appropriate tunnel placement. Computed tomography (CT) provides detailed images of intra-articular osseous anatomy. The objective of this study was to analyze by CT the position of femoral and tibial tunnels relative to intra-operative goals following arthroscopic-assisted PCL reconstruction. Nineteen patients who underwent single-bundle PCL reconstruction were evaluated 16 months post-operatively. Each underwent a CT scan and tunnel locations were identified in the coronal, sagittal, and axial planes. The coronal plane tibial tunnel location was within 5mm of the intra-operative goal (48% of the total tibial plateau width from the medial border of the plateau) in 16 patients (84%). The sagittal plane tibial tunnel location was within 5mm of the intra-operative goal (the middle of the posterior half of the retrospinal surface) in 14 patients (74%). In the sagittal plane, the femoral tunnel location was within 5mm of the intra-operative goal (10mm from in the distal articular margin of the medial femoral condyle) in 15 patients (79%). In the notch, the femoral tunnel was between 10:30 and 11:30 for left knees or between 12:30 and 1:30 for right knees (the intra-operative goal was 11 o'clock for left knees and 1 o'clock for right knees) in 18 patients (95%). Arthroscopic PCL reconstruction results in tunnel positions near intra-operative goals. Further work is necessary to define CT-specific criteria for the assessment of PCL tunnel position.

Does computer navigation system really improve early clinical outcomes after anterior cruciate ligament reconstruction? A meta-analysis and systematic review of randomized controlled trials

Inaccurate tunnel placement is an important cause of failure in conventional anterior cruciate ligament (ACL) reconstruction. Controversy currently exists over the usefulness of computer-assisted navigation systems in addressing this problem. Five randomized or quasi-randomized, controlled trials comparing computer-navigated versus conventional technique in ACL reconstructions until December 1, 2009 were identified through a systematical database search. The clinical outcomes of the trials were analyzed by Lachman test, pivot-shift test, International Knee Documentation Committee knee score, Lysholm score, and Tegner score. Mean difference or risk ratio with 95% confidence interval was calculated using a fixed-effects or random-effects model. Heterogeneity across the studies was also assessed. We found that the use of computer-assisted navigation systems led to additional operative time (8-17min). No significant differences between computer-navigated and conventional groups were found in terms of knee stability and functional assessment during short-term follow-up. The role of computer-assisted navigation systems on clinical performance and longevity needs further investigation in large sample, long-term randomized trials.

The use of intra-operative image intensifier control for the ACL surgeon

Tunnel placement during anterior cruciate ligament reconstruction surgery is an important factor in determining the outcome of surgery. Tibial and femoral tunnel placement depends on the experience of the operating surgeon in order to achieve an isometric graft position. We performed a case series to study how often tunnel placement was adequate, as perceived by the surgeon, and if intra-operative image guidance could improve tunnel position. Over 3 years, a single surgeon and his team operated on 55 patients using single bundle patellar tendon bone or hamstring graft. The surgeon placed the guidewires where he felt they would achieve an isometric graft position. A transtibial jig was used for femoral tunnel positioning. At each step, the guidewires were checked using an image intensifier and repositioned as necessary. The number of times that the guidewire position could be improved using the image intensifier was documented. Follow up was between 1 to 3 years. The tibial guidewire was repositioned in 13 out of 55 cases and the femoral guidewire in 16 out of 55 cases. Forty-five out of 55 patients returned to their pre injury state. There were no cases of graft failure in the follow up period. The study concludes that tunnel placement is not always successful despite the surgeon's perception of adequate placement. The use of an intra-operative image intensifier can help the surgeon to achieve accurate and reproducible tunnel placement in ACL reconstruction surgery. We recommend this technique to all surgeons carrying out such procedures.

Inter- and intraobserver reliability of the clock face representation as used to describe the femoral intercondylar notch

PURPOSE

To validate the use of the clock face reference as a reliable means of communicating femoral intercondylar notch position.

METHODS

A single red mark was made on ten identical left Sawbones femurs in the intercondylar notch at variable locations. Ten surgeons, who routinely perform ACL reconstructions, were presented the femurs in random order and asked to state the position of the mark to the nearest 30-min interval. Responses were recorded and then repeated 3 weeks later. The same 10 surgeons were presented with 30 actual arthroscopic photographs of the intercondylar notch, performed at 90° of knee flexion, with a probe pointing at various locations (10 knees; 3 photographs/knee) along the lateral aspect of the notch. The results were then analyzed with an ICC, Cronbach's alpha test, and descriptive statistics.

RESULTS

For the Sawbones, the ICC was 0.996 while individual physician's Cronbach's alpha test ranged from 0.954 to 0.999, indicating a very high interobserver and intraobserver reliability. The mean range of responses among the 10 surgeons was 1.6 h, SD 0.6. For the photographs, the ICC was also high at 0.997. There was a mean range of 1.1 h, SD 0.4, among surgeons.

CONCLUSIONS

The clock face method is commonly utilized for both placement of the femoral tunnel during ACL reconstruction as well as describing the location of the ACL femoral tunnel between communicating surgeons. Despite a high statistical interobserver correlation, there is significant range among different surgeons' responses. The present study questions the reliability of the clock face method for use between surgeons as a stand alone tool. Other methods also utilizing anatomic landmarks may be more accurate for describing intercondylar notch anatomy.

LEVEL OF EVIDENCE

III.

Anatomic double-bundle anterior cruciate ligament reconstruction, using CT-based navigation and fiducial markers

PURPOSE

Accurate placement of separate anteromedial and posterolateral bundle bone tunnels is crucial for anatomic, double-bundle anterior cruciate ligament (ACL) reconstruction. However, identifying the anatomic footprint at which to make the tibial and femoral bone tunnels is not a straightforward procedure. To overcome this problem, we used a CT-based navigation technique with a registration procedure based on fiducial markers (FMs).

METHODS

Preoperatively, 10 FM points were placed on skin around knee joint and scanned with CT. Imaging data of the knee were recorded on the computer system for preoperative registration and surgical planning. Intraoperatively, with a reference frame fixed to the distal medial aspect of femur and tibia, paired-point matching registration was performed with the use of points marked on skin through FM center holes. During tibial tunnel guide wire placement, tibial aiming guide with tracking device fed back the position of tip and direction of the guide wire on the three-dimensional (3D) tibia bone surface image and multiple image planes in real time. For the femoral side, the navigation pointer was placed at the footprint center with visual guidance of 3D image of lateral wall sagittal view on navigation monitor and marked with navigation awl.

RESULTS

The average registration accuracy of 22 consecutive patients was 0.7 ± 0.2 mm and 0.6 ± 0.2 mm for femoral and tibial bone, respectively. Most of the bone tunnel positions evaluated with 3D-CT image were confirmed to be accurately placed in reference to the preoperative plan. There was no damage to femoral condyle cartilage and no other complication.

CONCLUSION

This new CT-based computer navigation system opens the possibility for surgeons to plan bone tunnel positioning preoperatively and control it during technically demanding anatomic double-bundle ACL reconstruction.

Tunnel positioning in anterior cruciate ligament reconstruction: how long is the learning curve?

The purpose of this study is to investigate the effect of the learning curve on radiographic tunnel position. A consecutive series of the first 200 procedures of an orthopaedic surgeon over his initial 4years of independent practice were analysed for tunnel placement, based on radiographic appearance. An arthroscopic-assisted technique using patella tendon as graft material was performed in all cases. To establish femoral tunnels, a transtibial guide pin was used. The graft was secured with bioabsorbable screws. A Frik tunnel view and a strictly lateral radiograph were used to assess tunnel placements. Tunnel positioning was assessed using a computer-aided design, 2D software (Auto CAD2000(®)). To minimize measurement bias, radiographs were assessed three times or until deviations in all three measurements were less than 10%, and the three measurements were then averaged. Sagittal femoral tunnel placement improved significantly (P = 0.01) after the first 100 cases. Significant improvement (P = 0.05) in coronal femoral tunnel placement was observed after the first 75 cases. Significant improvement (P = 0.01) in sagittal tibial tunnel position was observed after the first 100 cases. Mean coronal tibial tunnel did not improve. Critical analysis in this consecutive series suggests that a caseload of approximately 100 procedures were necessary for this surgeon to refine his surgical technique beyond that acquired during formal training.

Comparative study on anterior cruciate ligament reconstruction: determination of isometric points with and without navigation

OBJECTIVES

To compare the accuracy of tunnel placement and graft isometry for anterior cruciate ligament reconstruction performed using a computer-assisted navigation system (Orthopilot) and using traditional instruments.

METHODS

The anterior cruciate ligament was removed intact from 36 pairs of human cadaver knees. From each pair, one knee was randomized to Group 1 (conventional) and the other to Group 2 (Orthopilot). An inelastic suture was then passed through the central points of the tibial and femoral tunnels. Neither of the tunnels was drilled. All knees were then dissected, and six parameters were obtained: distances from the tibial tunnel center to the 1) posterior cruciate ligament, 2) anterior horn of the lateral meniscus and 3) medial tibial spine; 4) distance from the femoral tunnel center to the posterior femoral cortex; 5) femoral tunnel coronal angle; and 6) variation of the distance from the femoral to the tibial tunnel with the knee extended and at 90 degrees of flexion.

RESULTS

The variation of the distance from the femoral to the tibial tunnel during flexion and extension was smaller in the Orthopilot group (better isometry) compared to the conventional group. There were no statistical differences in any other parameters between the groups, and all tunnels were considered to be in satisfactory positions.

DISCUSSION

The results obtained for anterior cruciate ligament reconstruction depend on precise isometric point positioning, and a navigation system is a precision tool that can assist surgeons in tunnel positioning.

CONCLUSION

No differences in tunnel position were observed between the groups. Nonetheless, better isometry was achieved in the Orthopilot group than with conventional instruments.

Development and in situ application of an adjustable aiming device to guide extra- to intraarticular tibial tunnel drilling for the insertion of the cranial cruciate ligament in dogs

OBJECTIVE

To develop and test an arthroscopic aiming device for extra- to intraarticular tibial tunnel drilling emerging at the center of the tibial insertion (CenterTib) of the cranial cruciate ligament (CCL) in medium to large breed dogs.

STUDY DESIGN

Descriptive experimental study.

SAMPLE POPULATION

Fifty-two cadaveric hind limbs of dogs >or=20 kg BW.

METHODS

The mediolateral position and craniocaudal position (ccPos) of CenterTib in relation to the caudomedial meniscotibial ligament were measured on photographs of 46 dissected tibial plateaus. The proximal tibial depth (TibDepth) was determined on lateral radiographs and its correlation with ccPos was assessed using linear regression analysis. Extra- to intraarticular arthroscopic tibial tunnel drilling was performed in 6 independent cadaveric stifles. A C-guide with an adjustable craniocaudal offset was constructed and adjusted according to ccPos estimated based on TibDepth. The position of the resulting bone tunnels was compared with the position of the CenterTib.

RESULTS

Pearson's correlation between TibDepth and ccPos was strong (R=0.86; P<.001). ccPos (y) as a function of TibDepth (x) can be expressed as y=-4.8+0.3x. Arthroscopic tunnel drilling resulted in a median deviation of the drill tunnels around the CenterTib of 1 mm.

CONCLUSION

The regression equation and aiming device permit localization and targeting of CenterTib during extra- to intraarticular tibial bone tunnel drilling in vitro.

CLINICAL RELEVANCE

The proposed technique may reduce tibial tunnel misplacement when performing intraarticular CCL repair using a tibial bone tunnel.

Anterior cruciate ligament tibial guide pin accuracy and surgical precision: comparing 3.0-mm and 2.4-mm guide pins

PURPOSE

The purpose of this study was to evaluate the accuracy of a 3.0-mm-diameter anterior cruciate ligament (ACL) tibial guide pin versus a standard, 2.4-mm drill-tipped guide pin. A secondary purpose was to evaluate surgeon precision in identifying the true (anatomic) center of the ACL tibial footprint using arthroscopic visualization.

METHODS

Five matched pairs of cadaveric knees were disarticulated, leaving a well-defined footprint of the ACL on the tibial plateau. The tibial footprint was digitally recorded by a bioengineer, and the true center of the footprint was calculated. Next, using arthroscopic visualization, a surgeon identified and marked his estimation of the true center of the ACL tibial footprint. This mark was then digitally recorded by the bioengineer and compared with the calculated center, allowing quantification of surgeon anatomic precision. Finally, under arthroscopic visualization, the surgeon was given 1 attempt to aim and drill the guide pin to his mark. Pin position was digitally recorded; the distance of the drill pin from the mark quantifies drill pin placement accuracy.

RESULTS

Mean accuracy for the 3.0-mm guide pin was 2.87 +/- 1.19 mm versus 6.98 +/- 1.29 mm for the 2.4-mm pin. The difference was significant (P = .005). Surgeon anatomic precision was 3.32 +/- 2.10 mm.

CONCLUSIONS

Our results show that a 3-mm ACL tibial guide pin is significantly more accurate than a 2.4-mm-diameter pin. The 3-mm pin accuracy is within the range of surgeon precision; the 2.4-mm pin accuracy is not.

CLINICAL RELEVANCE

Pin accuracy and surgeon precision are clinically relevant measures because anatomic tunnel placement is a determinant of ACL reconstruction outcome.

Transtibial versus anteromedial portal of the femoral tunnel in ACL reconstruction: a cadaveric study

The aim of this cadaveric study was to compare the transtibial versus the anteromedial portal with respect to the anatomic femoral positioning of the ACL attachment. Ten fresh frozen cadaveric knees were included in our study. A standard arthroscopy was performed and the normal ACL was partially cut through with arthroscopic scissors leaving a small footprint of 2 mm at the anatomical insertion area on the lateral femoral condyle. The femoral tunnel was drilled through the tibial tunnel and subsequently through the anteromedial portal. Using a probe with standard magnification, we measured the distances of the two femoral tunnels from the margin of ACL footprint arthroscopically. The femurs were then dissected and we measured the distances of the two tunnels from the posterior part of the lateral femoral condyle. The median arthroscopically measured distance of the centers of transtibial femoral tunnel and of the femoral tunnel through the anteromedial portal from the margin of the femoral ACL footprint were 6.20 mm and 2.80 mm respectively. The difference was statistically significant. After femoral dissection the median distance of the centers of the transtibial femoral tunnel and the femoral tunnel performed through the anteromedial portal from the border of the articular surface at the lateral femoral condyle was 6.10 mm and 5.25 mm respectively (p<0.001). Both measurements showed that ACL reconstruction technique through the anteromedial portal is more accurate compared to the transtibial technique.

Outcomes after conventional versus computer-navigated anterior cruciate ligament reconstruction

PURPOSE

The purpose of this prospective randomized study was to assess biomechanical, radiographic, and functional results after single-bundle anterior cruciate ligament (ACL) reconstruction by use of a navigation system.

METHODS

ACL reconstruction was performed by use of the OrthoPilot navigation system (B. Braun-Aesculap, Tuttlingen, Germany) in 40 patients (group 1); and in another 40 patients, surgery was done by the standard manual targeting technique (group 2). The anterior laxity was measured with a KT-1000 arthrometer (MEDmetric, San Diego, CA). Femoral and tibial tunnel position was evaluated radiologically according to the method described by Bernard and Hertel and by Harner et al., respectively. The questionnaire-based Lysholm and International Knee Documentation Committee scales were included to compare the functional state in both groups.

RESULTS

The knees in group 1 were as stable as those in group 2 during the arthrometer testing, with a lower value of dispersion. The postoperative Lysholm and International Knee Documentation Committee scores had the same value in both groups. Statistical differences existed with regard to anterior-posterior femoral tunnel placement when the navigated and standard techniques were compared; in the navigated group, more exact results were found. No significant complications were observed.

CONCLUSIONS

The only difference that we found between the navigated and standard groups was in radiographic tunnel position measurement. The computer-assisted navigation technique in our study resulted in more accurate tunnel placement in the femur (but not the tibia) than the traditional arthroscopic technique. However, the performed standard radiographic measurements are of limited precision in principle. Functional scales and stability tests gave similar results in both groups.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The prone kneeling view of the intercondylar notch for radiographic assessment of the femoral tunnel position in anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to verify the relevance of a novel radiograph, named the prone kneeling (PK) view of the intercondylar notch, for the assessment of femoral tunnel position in anterior cruciate ligament reconstruction.

METHODS

The PK view is taken with the subject prone, kneeling on the film, with the hip and knee joint flexed 90 degrees . The beam projects 20 degrees to the longitudinal axis of the femur posteroanteriorly. We used 5 human cadaveric femora in the experiment. A radio-opaque marker was applied in the intercondylar notch from the 12- to 8-o'clock position, which represented the tunnel position during arthroscopy. Radiographs simulating the anteroposterior (AP), tunnel, and PK view were obtained, and the positional data in angles were compared with the designated positions in the notch during arthroscopy.

RESULTS

From 12:00 to 11:00, all 3 radiographs gave comparable values to the true angle. At 10:30 and 10:00, only the PK view provided a comparable value whereas the other 2 radiographs yielded significantly different values. From 9:30 to 8:00, even though all 3 radiographs showed significantly different values from the true angle, the PK view was closest to the true angle, followed by the tunnel view and AP view.

CONCLUSIONS

The PK view shows the intercondylar notch with the femoral tunnel angle more accurately than the AP or tunnel view. This most closely represents the true angle of the femoral tunnel and is very similar to the angle seen at arthroscopy.

CLINICAL RELEVANCE

The position of the femoral tunnel seen on the postoperative plain AP radiograph might not appear identical to that determined during arthroscopy, probably because of the different knee position.

Differences in the placement of the tibial tunnel during reconstruction of the anterior cruciate ligament with and without computer-assisted navigation

BACKGROUND

Next to graft fixation, correct positioning of the tibial and femoral tunnel is a deciding factor for the clinical result of anterior cruciate ligament reconstruction surgery. Computer-assisted navigation has been proposed as a method to improve tunnel positioning.

PURPOSE

To examine the differences in tibial tunnel placement between cruciate ligament operations using manual and computer-assisted navigation.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Between December 2003 and April 2004, 53 athletes underwent anterior cruciate ligament reconstruction surgery with arthroscopic press-fit technique. The first group (group N; 24 athletes) were operated on with the aid of a navigation system (OrthoPilot, Aesculap AG & Co. KG, Braun), and the second group (group M; 29 athletes) were "manually" operated on. A lateral radiograph of the knee at maximum extension was used to determine the exact position of the tibial tunnel four days postoperatively. In the measurements, the anterior and posterior boundaries of the tibial tunnel, as well as the center of the tibial tunnel in relation to the maximum tibia anteroposterior diameter were evaluated (indicated in percent). An analysis of the tibial tunnel position proportional to the slope of the intercondylar roof was done to determine intercondylar impingement (method according to Howell). The centers of the tibial tunnels were compared with the "optimal" position noted in previous studies. The standard deviation was determined for both groups to determine the variance of placement.

RESULTS

The anterior tibial tunnel border was 19.4 mm in group M (29.7%) and 21.2 mm in group N (32.2%) (P = .18). The center of the tibial tunnel was located at 24.6 mm in group M (35.6%) and at 26.6 mm in group N (40.3%) (P = .19). In group M, the posterior tibial tunnel position was located at 30.2 mm (46.2%), and in group N at 32.2 mm (49.1%) (P = .21). When comparing the centers of the tibial tunnels with the optimal 44% found in previous studies, the value for group M (37.6%) varied significantly, while group N (40.5%) did not. However, there was no significant difference in the range variance for either group; the standard deviation was 6.9% (4.3 mm) for group M and 5.9% (3.5 mm) for group N. One athlete showed moderate impingement in group N, and two athletes in group M.

CONCLUSION

Assisted navigation offers good support for correct placement of the tibial tunnel, although experienced surgeons can achieve essentially the same positioning as surgeons using computer-assisted navigation. Whether it is advisable to implement this procedure in daily surgical routine should be decided based on clinical results.

Correlation between radiological and clinical findings after anterior cruciate ligament reconstruction

Introduction. In the last two decades, the gold standard for anterior cruciate ligament reconstruction is the bone-patellar tendon-bone graft procedure. Correct position of the bone-patellar tendon-bone graft significantly affects the postoperative knee stability. The aim of this study was to establish if and how clinically measured knee stability is associated with radiographic position of bone-patellar tendon-bone graft in the femoral and tibial bones. Material and methods. The prospective study included 39 patients, 30 men and 9 women. We analyzed and compared results of clinical and radiographic examinations prior to and 2 years following surgery. Results. The mean arthrometric difference between the anterior tibial movement prior to surgery was 11,2mm and 2,4mm (p<0,05) after surgery. The preoperative Tegner and Lysholm score was 1,49, and postoperative 8,23 (p<0,05). The preoperative Lysholm-Gillquist scale was 51,56 and postoperative 97,74 (p<0,05). The International Knee Documentation Committee (IKDC) scores were as follows: grade A in 32 patients (84.6%), grade B in 5 patients (12.8%), and grade C in 1 patient (2.6%). By comparison of IKDC scores and radiographic parameters (M1 - M10) of anterior-posterior and profile views, a statistical significance was found only between IKDC and M9 index (sagittal femoral index OR?/RR? x 100). Discussion. By using bone-patellar tendon-bone grafts, it is not possible to entirely achieve anatomical positions. Correct graft position within the bone tunnels is of great significance concerning knee stability after anterior cruciate ligament reconstruction. Conclusion. Correlation between radiological and clinical findings after anterior cruciate ligament reconstruction in our 39 patients shows that only the position of the graft affects the clinical outcome. Posterior graft location provides better clinical outcome and knee stability. On the other hand, anterior location is associated with worse postoperative IKDC scores, unstable knee and worse clinical outcome. .

Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes

As many as 175,000 anterior cruciate ligament (ACL) reconstructions are performed annually in the United States at a cost >1 billion dollars. Estimates of the rate of revision surgery are as high as 10%-20%, potentially resulting in as many as 35,000 revisions a year. In addition, errors that are not obvious at short-term or mid-term follow-up may have significant long--term effects in young patients. Studies have demonstrated that the majoriity of visions are related to technical errors, primarily tunnel placement. Computer-aided navigation systems provide enhanced precision in tunnel placement and may reduce the rate of revision surgery. Computer-aided systems can provide valuable data on rotational and translational laxity of the knee.