Abstract
Background
Drilling the femoral and tibial tunnels at their anatomical locations are critical for good outcomes and involve seeing the footprints well. We intended to compare two techniques of drilling the tunnels and the patient-reported outcomes and knee stability of patients undergoing single bundle ACL reconstruction using 3D CT to evaluate if the tunnels were anatomical or not.
Materials and Methods
Sixty single bundle ACL reconstructions were analyzed, 30 each with Technique A and B. Pre-operative and after a minimum 27 month follow-up Lysholm, IKDC, Tegner score, hop test, and Lachman test were noted. 3D CT was done to classify femoral tunnels positions as being well placed, slightly or grossly misplaced and tibial tunnels as optimal or suboptimal and compared.
Results
Sixty ACL reconstructions had full follow-up with a mean follow-up of 34 months. There was no significant difference between tunnel positions between the two techniques. Well-placed femoral tunnel had better Lysholm score (62.2 ± 16.2 v/s 48.5 ± 17.2, p 0.002) and IKDC score (62.5 ± 14.3 v/s 52.7 ± 15.1, p 0.012).). Those who had their surgeries within 3 months of their injury had better hop test (4.4 ± 0.9 v/s 3.9 ± 1, p 0.034) and IKDC scores (62.5 ± 15.8 v/s 33.2 ± 13.8, p 0.026) as compared to those that had surgery done after 3 months
Conclusion
Tibial tunnel positions were optimal in most cases and did not differ between the two techniques. Well-placed femoral tunnels and surgeries done within 3 months of the injury produced best results.
Keywords: ACL, ACL Reconstruction, Anterior Cruciate Ligament Reconstruction, Biological ACL Reconstruction, Stump Preservation ACL Reconstruction, 3D CT, Tunnel position, Transportal ACL reconstruction, Accessory portal, PROM post-ACL
Introduction
Anatomically reconstructed grafts have been shown to be biomechanically better than non-anatomical grafts [1,2]. They also have better stability and earlier recovery than non-anatomically reconstructed grafts [3]. To achieve more anatomical graft position, Anterior Cruciate Ligament (ACL) surgery has evolved over time. ACL reconstruction is done using a single or double bundle techniques and transportal or transtibial techniques. The transportal technique is shown to have distinct advantages as compared to transtibial techniques as it produces more anatomical grafts [4, 5]. However there have not been significant differences in outcomes of single and double bundle reconstructions [6–11]. The ideal location of the femoral and tibial tunnels is where the native ACL was, but in chronic cases, the tibial and femoral remnants may not be present and we rely on anatomical landmarks to make our tunnels. These landmarks are based on previously done studies [12, 13].
There have been studies in the past to evaluate the role individual factors on patient-reported outcome measures and stability post-ACL reconstruction. Tunnel position has been found to be an important variable in these outcomes. Tunnel positions can be assessed via X-ray and computed tomography (CT) scan with CT being potentially more accurate as it gives a three-dimensional picture of the femoral and tibial tunnel apertures [14, 15]. There have been studies done in the past to assess femur and tibial tunnels positions in various techniques of doing ACL reconstructions [16, 17]. Femoral tunnel position has been shown to influence patient-reported outcomes more than the tibial tunnel position [18]. Tunnel malposition is an iatrogenic complication and studies have been done in the past which showed that when viewing the femoral footprint end on while drilling the femoral tunnel produced tunnels that were more anatomic, but it was not statistically significant [19].
Studies in the past have focused on individual tunnel positions and based their acceptable tunnel positions on the basis of the variation of individual tunnels from a set standard deviation [20]. However we have classified our femoral and tibial tunnels based on whether they are optimal or not based on previously done studies [21]. Apart from just tunnel positions, we have tried to compare individual surgical and constitutional factors that may affect outcomes in our cohort population.
The ultimate result of a surgery is measured by the patients return to activity and pre-operative functional levels that may be different for different individuals. However, instrumented objective methods can also be used to measure stability of individual ligaments. Studies in the past have shown that even though there may not be statistically significant differences in the objective arthrometric measurement before and after surgery, subjective scores do show a significant improvement [20].
The primary objective of this study was to evaluate if optimal femoral and tibial tunnel position translated into better stability and post-operative outcome measures. The secondary objective was to evaluate if viewing the tibial footprint from a high anteromedial portal while identifying and drilling it gives a more anatomical tunnel position.
Materials and Methods
A total of 60 patients underwent arthroscopic ACL reconstruction between Nov 2017 and Oct 2018 who fulfilled the criteria of this study. Our inclusion criteria was single bundle ACL reconstructions done by a single surgeon, the first author VM in complete ACL tears using semitendinosus and gracilis grafts fixed with a particular button on the femur and an interference screw on the tibia in all cases. Clinical and Magnetic Resonance Imaging (MRI) was used to diagnose the ACL tear, meniscus tear, or any associated injuries. Patients with multiligamentous knee injuries, tibial avulsion, osteoarthritis, previous femoral fractures, and congenital femoral and tibial abnormalities were excluded from the study. All patients had a single bundle ACL reconstruction. Pre-operative Lachman (International Knee Documentation Committee) IKDC, Tegner, hop test were done 24 h before surgery and at a minimum 27 month follow-up. Age, Body Mass Index (BMI), and time since injury were also noted in the patients. The ages was classified into < 25 or > 25 years, BMI into < 25 or > 25, and times since injury into < 3 months or > 3 months.
Meniscus procedures were classified into medial meniscectomies, lateral meniscectomies, medial meniscus repairs, or lateral meniscus repairs at the time of arthroscopy. Cases where chondral lesions were present were excluded. Graft diameters were noted at the time of surgery.
Surgical Technique [19]
A single bundle ACL reconstruction using semitendinosus and gracilis grafts was done in all cases. Two techniques were used to drill the femoral tunnel, either viewing through a high anteromedial portal and drilling through a far medial portal (Technique B) or viewing from a high anterolateral portal and drilling from a far medial portal (Technique A). The surgeon intended to drill the tunnel at a distance of 5 mm from the posterior articular margin and 5 mm from the inferior margin of the lateral aspect of the notch. The tibial tunnel was drilled at the centre of the tibial stump which was preserved, along the posterior border of the anterior horn of the lateral meniscus either viewing from the high anterolateral portal (Technique A) or the high anteromedial portal (Technique B) Figs. 1, 2.
Fig. 1.
Guide pin tip at the centre of the ACL tibial stump seen through the high anteromedial portal
Fig. 2.
Graft seen passing from the tibia to the femur viewing from the high anteromedial portal
Post-operative 3D CT Evaluation
The post-operative three-dimensional (3D) CT scan of the knee were done within a week of the arthroscopy and femoral and tibial tunnel positions was evaluated.
Femoral Tunnel Evaluation
A true lateral view of the medial wall of the lateral femoral condyle with neutral rotation was reconstructed and the medial condyle subtracted to see the lateral wall of the notch. The femoral tunnel position was evaluated using the quadrant method by Bernard et al. [22]. A reference frame was drawn with the superior border at the Blumensaat’s line of the intercondylar notch and inferior border at the lowest margin of the lateral wall of the intercondylar notch. The anterior and posterior borders of the frame were drawn touching the anterior most and posterior most points of the lateral wall of the intercondylar notch, respectively. The footprint was covered by the best-fit circle using the region-of-interest tool (ROI) in the CT software that covered all borders of the femoral tunnel. After marking the centre of the circle, perpendiculars were drawn to the length and breadth of the rectangle. DS represents distance from centre to superior border and DP the distance from centre to posterior border (Fig. 3). The individual tunnels were categorized according to their relationship with the lateral inter condylar ridge. Type I (well-placed) tunnels, Type II (slightly malpositioned), and Type III (grossly malpositioned) were those located superior and anterior to the ridge [19].
Fig. 3.
Technique to determine femoral tunnel position on a 3D CT image of the lateral wall of the femoral notch
Tibial Tunnel Position (Fig. 4)
Fig. 4.
Technique to determine tibial tunnel position on a 3D CT scan
A craniocaudal view of the upper surface of the tibia was obtained after subtracting the femur and patella from the 3D CT image of the knee. A reference frame was drawn aligned with medial-to-lateral and anterior-to-posterior anatomical tibial axes. The total width of the tibial axes was between the anterior-to-posterior and medial-to-lateral distance. A region-of-interest tool was used to fit the best-fit circle on the tibial aperture and its centre was marked. A perpendicular was drawn from the centre of tibial aperture to the anterior (DA) and medial border (DM) of this grid and noted [21]. The individual tunnels were categorized into optimal or suboptimal, DA < 31 or > 44.2 and DM < 36.3 or > 52 was considered suboptimal based on previous literature. Even one measurement out of this range classified the tunnel as sub optimal.
Rehabilitation
Those patients that had an ACL or an ACL with meniscectomy were allowed to bear weight as tolerated on post op Day 1. Static quadriceps and range of motion exercises were begun after 24 h of the procedure. The patient used crutches for 10 days till they felt confident of walking independently and the quadriceps had started contracting well. No running, jogging, or sports was allowed for 6 months post-surgery. Driving was allowed after 1 month of the procedure. In those that had a meniscus repair, the only difference in the rehabilitation was that they were kept non weight bearing for 6 weeks with a range of motion brace. Range of motion was commenced after 24 h but limited to 0–90° of flexion for 6 weeks. The rest of the rehab was same.
Statistical Methods
Statistical analysis was performed using SPSS Statistical Software version 22.0 and R.3.2.0. Two-sample t test was used for the comparison of means of improvement in scores between group created based on Quality of treatment, Tibial Quality, Injury to Surgery month. One-way ANOVA (Analysis of variance) was used for comparison of means of improvement in scores for Repair Type variable. P value of < 0.05 was considered significant.
Results
A total of 60 knees were evaluated (52 of them right and 8 left knees). There were 41 male and 19 female patients. The mean follow-up was 34 months with minimum follow-up of 27 months. There were 32 Type I femoral tunnels and 28 Type II femoral tunnels and no Type III tunnels (Table 1). There were 52 optimal and 8 sub optimal tibial tunnels. Technique A had 24 optimal tunnels and Technique B had 28 optimal tunnels (Table 1). The mean DM distance was 43.03 ± 1.973 in Technique A and 43.43 ± 1.959 in Technique B. The DA in Technique A was 35 0.67 ± 5.168 and 38.32 ± 4.327 in Technique B with no statistically significant difference between the two techniques p 0.434 (Fig. 5).
Table 1.
Number of Type I & II femoral tunnels, optimal and suboptimal tibial tunnels overall, and optimal tibial
| Femoral type 1 tunnels | 32 |
| Femoral type 2 tunnels | 28 |
| Total optimal tibial tunnels using both techniques | 52 |
| Total suboptimal tibial tunnels using both techniques | 8 |
| Technique A optimal tibial tunnels | 24 |
| Technique B optimal tibial tunnels | 28 |
Fig. 5.
Mean tibial tunnel positions by the two techniques versus Tsukada et al. and Florent et al. that are the other two 3D CT-based studies
Other than the preop Lysholm score which was lower in the Type I femoral tunnel group (32.4 ± 16.2 v/s 43.4 ± 18, p 0.016), there was no statistically significant difference in the postop Lysholm score, pre- and postop Lachman test, pre- and postop hop test, pre- and postop Tegner score, pre- and postop IKDC score, age, and BMI between Type 1 and Type 2 tunnels and graft diameter.
However, there was a statistically significant difference in the improvement of the Lysholm score (62.2 ± 16.2 v/s 48.5 ± 17.2, p 0.002) and the IKDC score (62.5 ± 14.3 v/s 52.7 ± 15.1, p 0.012) post-surgery in those with good femoral tunnels (Table 2). There was no statistically significant improvement in any of the outcome measures when the optimal and suboptimal tibial tunnels were compared. There was also statistically significant improvement in the Lysholm score of patients who had an optimal tibial tunnel with a Type 1 Femoral tunnel in comparison to an optimal tibial tunnel and Type II femoral tunnel (61.3 ± 15.7 v/s 50.9 ± 17.6, p 0.031) (Table 3).
Table 2.
Comparison of improvement in scores (post–pre) by type of femoral tunnel
| Parameters | PROMs and stability scores | ||
|---|---|---|---|
| Type I | Type II | p value | |
| Lysholm score | 62.2 ± 16.2 | 48.5 ± 17.2 | 0.002 |
| Hop test | 4.2 ± 0.9 | 4.0 ± 1.0 | 0.435 |
| Tegner | 4.0 ± 1.2 | 3.6 ± 1.1 | 0.181 |
| IKDC | 62.5 ± 14.3 | 52.7 ± 15.1 | 0.012 |
| Lachman | 2.6 ± 0.6 | 2.2 ± 0.8 | 0.062 |
Table 3.
Comparison of improvement in scores (post–pre) by quality in optimal tibial tunnels
| Parameters | Quality of treatment | ||
|---|---|---|---|
| Type I | Type II | p value | |
| Lysholm score | 61.3 ± 15.7 | 50.9 ± 17.6 | 0.031 |
| Hop test | 4.2 ± 0.9 | 3.9 ± 1.1 | 0.421 |
| Tegner | 3.9 ± 1.1 | 3.6 ± 1.2 | 0.337 |
| IKDC | 61.5 ± 13.4 | 55.2 ± 14.2 | 0.113 |
| Lachman | 2.5 ± 0.6 | 2.2 ± 0.8 | 0.145 |
Those that were < 25 years did not have any statistically significant improvement in any outcome measures as compared to those over 25. Those that had their surgery within 3 months of the index injury had better hop test (4.4 ± 0.9 v/s 3.9 ± 1, p 0.034) and IKDC scores (62.5 ± 15.8 v/s 33.2 ± 13.8, p 0.026) as compared to those that had surgery done after 3 months. There were no statistically significant differences in outcomes of those with BMI < or > 25, those that had lateral/medial meniscus repairs or excisions or inpatients with graft diameter > or < 9 mm as all the patients had a graft > 8 mm.
Complications
Two patients had stitch abscesses at the graft harvest site that healed with antibiotics and dressing. One patient had persistent pain in the medial compartment knee at 30 month follow-up that was diagnosed as early medial compartment osteoarthritis of the knee. The knee was stable, the femoral tunnel was Type II, and the tibial tunnel was optimal.
Discussion
ACL reconstruction has evolved over the years into a more anatomical technique so as to replicate the original ACL origin and insertion. Tunnel position has taken preponderance in recent times as it has been identified as one of the most important aspect of the procedure that determines outcomes [23]. Outcomes have been measured on the basis of patient-reported outcome measures, stability of the knee, and activity levels.
This study used two techniques of doing an ACL reconstruction, which were different from each other as viewing, and drilling from the medial side gives an end on view of the femoral footprint and shows the whole course of the ACL graft from tibia to its femoral attachment in one frame. However, the other technique views the femoral footprint from the side, and hence, it was hypothesized that the femoral tunnel position may be less anatomic. Though the number of optimal tibial tunnels and well-placed Type 1 femur tunnels was more in Technique B, this was not statistically significant [19]. Future studies with larger numbers should be done to evaluate whether doing an ACL reconstruction with viewing through a high anteromedial portal and drilling through a low far medial portal produces better tunnel positions.
The results of our study seem to suggest that femoral tunnel position and time since injury are the most important factors affecting outcomes. Tibial tunnel position was more or less constant in the study with most of the tunnels being optimally placed at the location. This could be the reason as our technique of drilling the tibial tunnel used a definitive anatomical landmark as its location, which does not change with flexion or extension of the knee. Using the SAMMBA technique of remnant preservation at the tibial stump is shown to give near anatomic tibial tunnels, which may be another reason for more consistent tibial tunnels. This suggests that the view of the tibial footprint is more or less consistent with either portal being used to view it and is consistent with the current literature [19]. The femoral tunnel position was made 5 mm from the posterior and inferior articular margin, which could make the tunnel position change depending on the degree of knee flexion. This may be the cause of more variability in the tunnel position as compared to the tibia, though none of the tunnels were grossly misplaced. The improvement in Lysholm and IKDC scores were significantly better in those patients who had well-placed femoral tunnel as compared to those with a slightly misplaced tunnel position indicating the importance of avoiding misplaced tunnels. Techniques that provide better visualization of the femoral footprint need evaluation in larger series of patients to have more consistent tunnel positions.
The age and BMI of the patients did not seem to affect outcomes, as most of the patients were of a similar age group and there were no obese patients in this subset. There was no statistically significant difference in the age and BMI of patients in the tunnel groups compared.
Patients that had their operation within 3 months of their injury had better IKDC and hop test scores. This could be attributed to the fact that lesser injuries to surrounding structures or their capacity to heal are better when operated upon early. A chronic ACL deficient knee may lead to degenerative changes and injury to secondary stabilizers over a period of time worsening outcomes.
Meniscus surgery did not seem to affect outcomes as in most cases, there was either no meniscus surgery or they were repaired, that is shown to preserve the biomechanics of the knee. The minority of cases that had a partial meniscectomy was smaller in number and could be a possible reason for not influencing outcomes. Also, the follow-up was for 34 months, longer follow-up might be necessary to conclusively identify the role of meniscus surgery on outcomes. Studies in the past have used CT and X-rays to measure tunnel positions as well as outcome measures for stability and PROM’s post-ACL reconstruction. Behrend et al. that analyzed 50 ACLs done by 17 surgeons of different experience levels by doing X-rays for tunnel position and IKDC scores for PROMs and the KT 1000 for stability and showed that tibial malpositions were better tolerated than femoral malpositions, which was consistent with our study [24]. More experienced surgeons had better outcomes; our study had the advantage of a single surgeon (VM) doing all the surgeries. Sadoghi et al. analyzed single bundle BPTB and double bundle hamstring ACLR’s with short 1 year follow-up showed better stability and PROMs when the reconstruction was more anatomical. Mild alterations within the anatomic ACL footprint did not have significantly different outcomes. This study used 2 SD from the mean value of the tunnel positions as the cut off for the tunnel being anatomic and this was not compared to any anatomic study or previous studies about the ideal tunnel position. Our study took all previously done studies into consideration before classifying the tunnel on the tibial side as anatomic or non-anatomic and did not base it on any mean or SD of our own tunnels in the series, whereas classifying the femoral tunnels was done based on an anatomic classification system published earlier. Kazemi et al. classified femoral tunnels based on the angle they made on an AP radiography with the anatomic axis of the femur as low 30–45° or high 45–60°, and found that low posterior tunnels had higher knee scores at a mean 23.6 month follow-up [18]. This does not take into consideration the exact tunnel position but just the trajectory of the tunnel in a tunnel-view X-ray that does not relate to the anatomic insertion point in the notch unlike our study [18]. Two other studies have reported on the effect of tunnel positions using 3D CT on stability and patient-reported outcomes. However, the follow-up was only for 12 and 30.3 months only. They also just reported on the PROMs and stability based on individual tunnel positions and not on whether they were considered anatomic or not [3, 20]. Our study also had the advantage of having the longest mean follow-up as compared to previously done studies.
There were a few drawbacks of our study the inclusion of cases with meniscus surgery could have potentially affected outcomes. Also not having an objective measure like a KT 1000/arthrometer machine to measure translation could make AP stability subjective. However, the hop test is a practical measure of stability with the whole body weight being on the operated limb while hopping [25]. Also, previously done studies have proven that though objective methods of stability may not change significantly, subjective scores do improve and ultimately patient satisfaction is of paramount importance and an improvement in subjective scores are indicative of that.
None of the patients had persistent instability or any major complications only minor ones like two stitch abscesses, indicating that tunnels that are not grossly misplaced produced stable knees in this study.
We can conclude that in our subset of patients, femoral tunnel position was the single most important factor affecting outcomes post -ACL reconstruction.
Declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical standard statement
This study was approved by the Max Healthcare Ethics Committee.
Informed consent
Informed consent was taken from every patient recruited in this study as per the protocol sanctioned by the Max Healthcare Ethics Committee.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Vikram A. Mhaskar, Email: drvikrammhaskar@gmail.com
Yogesh Jain, Email: jainy134@gmail.com.
Pankaj Soni, Email: pankaj.soni0206@gmail.com.
Rajendra Fiske, Email: rajendra07115@gmail.com.
Jitendra Maheshwari, Email: Jitendra.Maheshwari@maxhealthcare.com.
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