Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament

Purpose

To investigate the optimal starting points for drilling on the lateral femoral condyle for better coverage of the anatomical footprint of the anterior cruciate ligament (ACL) using the outside-in (OI) technique in a single-bundle ACL reconstruction.

Methods

Femoral tunnel drilling was simulated on three-dimensional bone models from 40 subjects by connecting the centre of the ACL footprint with various points on the lateral femoral surface. The percentage of the femoral footprint covered by apertures of the virtual tunnel sockets with 9 mm diameter was calculated for each tunnel.

Results

The mean percentages of the femoral footprint covered by the apertures of the virtual tunnel sockets were significantly higher when drilled at 2 and 3 cm from the lateral epicondyle on a 45° line and a 60° line anterior from the proximal–distal axis than the other points. However, articular cartilage damage was occurred in nine subjects at 3 cm on a 60° line and eight subjects at 3 cm on a 45° line. Posterior wall blowout occurred in five subjects at 3 cm on a 45° line. Thus, OI drilling at 3 cm from the epicondyle has a risk of these complications.

Conclusion

During the OI drilling of the femoral tunnel, connecting the centre of the anatomical footprint of the ACL and the entry drilling point at 2 cm from the lateral epicondyle on between the 45° line and the 60° line anterior from the proximal–distal axis provides an oval-shaped socket aperture that covers and restores the native ACL footprint as nearly as possible.

Level of evidence

III.

     

Sagittal femoral condyle morphology correlates with femoral tunnel length in anatomical single bundle ACL reconstruction

Purpose

The purpose of this study was to reveal the correlation between femoral tunnel length and the morphology of the femoral intercondylar notch in anatomical single bundle anterior cruciate ligament (ACL) reconstruction using three-dimensional computed tomography (3D-CT).

Methods

Thirty subjects undergoing anatomical single bundle ACL reconstruction were included in this study (23 female, 7 male: average age 45.5?±?16.7). In the anatomical single bundle ACL reconstruction, the femoral and tibial tunnels were created close to the antero-medial bundle insertion site with trans-portal technique. Using post-operative three-dimensional computed tomography (3D-CT), accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the transepicondylar length (TEL), notch width index, notch outlet length, the notch area (axial), length of Blumensaat’s line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analyzed. Tunnel placement was also evaluated using a Quadrant method.

Results

The average femoral tunnel length was 35.4?±?4.4 mm. The average TEL, NWI, notch outlet length, and the axial notch area, were 76.9?±?5.1 mm, 29.1?±?3.8%, 19.5?±?3.9 mm, and 257.4?±?77.4 mm², respectively. The length of Blumensaat’s line and the height and area of the lateral wall of the femoral intercondylar notch were 33.8?±?3.2 mm, 22.8?±?2.3 mm, and 738.7?±?129 mm², respectively. The length of Blumensaat’s line, the height, and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 23.4?±?4.5% in a shallow-deep direction and 35.4?±?8.8% in a high-low direction.

Conclusion

The length of Blumensaat’s line, height, and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single bundle ACL reconstruction. For clinical relevance, these parameters are useful in predicting the length of the femoral tunnel in anatomical single bundle ACL reconstruction for the prevention of extremely short femoral tunnel creation.

Level of evidence

Case controlled study, Level III.

     

Calcium phosphate-hybridized tendon grafts reduce femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction

Purpose

This study aimed to clarify the effect of calcium phosphate (CaP)-hybridized tendon grafting versus unhybridized tendon grafting on the morphological changes to the bone tunnels at the aperture 1 year after anatomic single-bundle anterior cruciate ligament (ACL) reconstruction.

Methods

Seventy-three patients were randomized to undergo the CaP (n = 37) or the conventional method (n = 36). All patients underwent computed tomography (CT) evaluation 1 week and 1 year post-operatively. The femoral and tibial tunnels at the aperture were evaluated on reconstructed 3D CT images. Changes in the cross-sectional area (CSA) and diameters of the femur and the tibia, and the translation rate of the tunnel walls and the morphological changes of both tunnels were assessed.

Results

There was a significant reduction in the increase in the CSA and the anterior–posterior and proximal–distal tunnel diameters on the femoral side in the CaP group as compared with the conventional group. On the femoral side, the translation rate of the posterior wall was significantly larger in the CaP group than in the conventional group, whereas the translation rate of the distal wall was significantly smaller in the CaP group than in the conventional group.

Conclusions

As compared with the conventional method, the CaP-hybridized tendon graft reduced bone tunnel enlargement on the femoral side 1 year after anatomic single-bundle ACL reconstruction due to an anterior shift of the posterior wall and reduced distal shift in the femoral bone tunnel. Clinically, the CaP-hybridized tendon grafts can prevent femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction.

Level of evidence

I.

     

Anatomic double bundle ACL reconstruction outperforms any types of single bundle ACL reconstructions in controlling dynamic rotational laxity

Purpose

To compare the different types of ACL reconstructions in terms of knee dynamic laxity evaluated by acceleration.

Methods

Sixteen fresh frozen cadaveric knees were used. Pivot shift test was manually performed while monitoring the tibial acceleration by use of a triaxial accelerometer. The test was repeated before and after the ACL resection and reconstruction. Three types of ACL reconstruction were tested: (1) Anatomic Single-Bundle reconstruction (n = 8), the graft was placed at the center of the ACL footprint for the both femoral and tibial sides (tunnel diameter: 8mm); (2) Conventional Single-Bundle reconstruction (n = 8), the graft was placed from the tibial PL footprint to femoral high AM position (tunnel diameter: 8mm) and (3) Anatomic Double-Bundle reconstruction (n = 8). The acceleration in each of three x-y-z directions and the overall magnitude of acceleration was calculated to evaluate dynamic rotational laxity and compared between different ACL reconstructions.

Results

The overall magnitude of acceleration was significantly different between ACL intact and deficient knees (p < 0.0001). The acceleration was reduced by the DB ACL reconstruction to the intact level (n.s.), but the two SB ACL reconstruction failed to achieve the intact level of the acceleration (p = 0.0002non-anatomic SB, p < 0.0001 anatomic SB).

Conclusion

The anatomic DB reconstruction better restores dynamic rotational laxity when compared to the SB ACL reconstructions no matter if the tunnel placement was anatomic. The anatomic DB reconstruction better restores dynamic rotational laxity when compared to both anatomic and non-anatomic SB ACL reconstruction. For this reason anatomic DB ACL reconstruction is recommended for cases where rotational laxity is an issue.

     

Post-operative 3D CT feedback improves accuracy and precision in the learning curve of anatomic ACL femoral tunnel placement

Purpose

To evaluate the feedback from post-operative three-dimensional computed tomography (3D-CT) on femoral tunnel placement in the learning process, to obtain an anatomic anterior cruciate ligament (ACL) reconstruction.

Methods

A series of 60 consecutive patients undergoing primary ACL reconstruction using autologous hamstrings single-bundle outside-in technique were prospectively included in the study. ACL reconstructions were performed by the same trainee-surgeon during his learning phase of anatomic ACL femoral tunnel placement. A CT scan with dedicated tunnel study was performed in all patients within 48 h after surgery. The data obtained from the CT scan were processed into a three-dimensional surface model, and a true medial view of the lateral femoral condyle was used for the femoral tunnel placement analysis. Two independent examiners analysed the tunnel placements. The centre of femoral tunnel was measured using a quadrant method as described by Bernard and Hertel. The coordinates measured were compared with anatomic coordinates values described in the literature [deep-to-shallow distance (X-axis) 28.5%; high-to-low distance (Y-axis) 35.2%]. Tunnel placement was evaluated in terms of accuracy and precision. After each ACL reconstruction, results were shown to the surgeon to receive an instant feedback in order to achieve accurate correction and improve tunnel placement for the next surgery. Complications and arthroscopic time were also recorded.

Results

Results were divided into three consecutive series (1, 2, 3) of 20 patients each. A trend to placing femoral tunnel slightly shallow in deep-to-shallow distance and slightly high in high-to-low distance was observed in the first and the second series. A progressive improvement in tunnel position was recorded from the first to second series and from the second to the third series. Both accuracy (+52.4%) and precision (+55.7%) increased from the first to the third series (p < 0.001). Arthroscopic time decreased from a mean of 105 min in the first series to 57 min in the third series (p < 0.001). After 50 ACL reconstructions, a satisfactory anatomic femoral tunnel was reached.

Conclusion

Feedback from post-operative 3D-CT is effective in the learning process to improve accuracy and precision of femoral tunnel placement in order to obtain anatomic ACL reconstruction and helps to reduce also arthroscopic time and learning curve. For clinical relevance, trainee-surgeons should use feedback from post-operative 3DCT to learn anatomic ACL femoral tunnel placement and apply it appropriately.

Level of evidence

Consecutive case series, Level IV.

     

Bone-to-bone integrations were complete within 5 months after anatomical rectangular tunnel anterior cruciate ligament reconstruction using a bone–patellar tendon–bone graft

Purpose

Anterior cruciate ligament (ACL) reconstruction using a bone–patellar tendon–bone (BTB) graft is known to provide secure fixation due to the direct bone-to-bone integration of the bone plug and bone tunnel. It is important to know the time required for bone integration when designing the postoperative rehabilitation protocol or deciding when the patient can return to competition-level activity, especially if the patient is an athlete. However, because reports are scarce, the period necessary for bone-to-bone integration after ACL reconstruction using a BTB graft remains unclear. The purpose of this study was to clarify this issue. It was hypothesised that ACL reconstruction using a BTB graft via an anatomical rectangular tunnel would help in the integration between bone plugs and bone tunnels on both the femoral and tibial sides after at least 6 months, at which point basic exercises similar to pre-injury sporting activity levels can be resumed.

Methods

This study included 40 knees treated with ACL reconstruction using a BTB graft via anatomical rectangular tunnel reconstruction between 2013 and 2014 in a single institute. The integration between bone plugs and bone tunnels was evaluated using multi-slice tomosynthesis, which is a technique for producing slice images using conventional radiographic systems, at 1, 3, and 5 months postoperatively. All procedures were performed by two experienced surgeons. Bone integration was evaluated by two orthopaedic doctors.

Results

The rates of integration of the bone plug and femoral bone tunnel on tomosynthesis at 1, 3, and 5 months postoperatively were 0, 55, and 100%, respectively. On the tibial side, the corresponding rates were 0, 75, and 100%, respectively. The rate of integration on the tibial side was significantly higher than that on the femoral side at 3 months postoperatively (p?=?0.031).

Conclusions

Bone-to-bone integration on the femoral and tibial sides was complete within 5 months after surgery in all cases. Since the time required for bone integration is important in designing the postoperative rehabilitation approach, these results will serve as a useful guideline for planning rehabilitation protocols.

Level of evidence

IV.

     

Peri-anterior cruciate ligament reconstruction femur fracture: a biomechanical analysis of the femoral tunnel as a stress riser

Purpose

Sixteen case reports of distal femur fractures as post-operative complications after anterior cruciate ligament (ACL) reconstruction have been described in the literature. The femoral tunnel has been suggested as a potential stress riser for fracture formation. Additionally, double bundle ACL reconstructions may compound this risk. This is the first biomechanical study to examine the significance of a stress riser effect of the femoral tunnel(s) after ACL reconstruction. The hypotheses tested in this study are that the femoral tunnel acts as a stress riser for fracture and that this effect increases with the size of the tunnel (8 mm vs. 10 mm) and with the number of tunnels (1 vs. 2).

Methods

Femoral tunnels simulating single bundle (SB) hamstring graft (8 mm), bone-patellar tendon-bone graft (10 mm), and double bundle (DB) ACL reconstruction (7, 6 mm) were drilled in fourth-generation saw bones. These three experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure.

Results

All fractures occurred through the tunnels in the DB group, whereas fractures did not consistently occur through the tunnels in the SB groups. The mean fracture load was 6,145N ± 471N in the native group, 5,691N ± 198N in the 8 mm SB group, 5,702N ± 282N in the 10 mm SB group, and 4,744N ± 418N in the DB group. The mean fracture load for the DB group was significantly lower when compared to the native, 8 mm SB, and 10 mm SB groups independently (P value = 0.0016, 0.0060, and 0.0038, respectively). The mean fracture loads for neither SB groups were not significantly different from the native group.

Conclusions

An anatomically placed femoral tunnel in single bundle ACL reconstruction in our experimental model was not a significant stress riser to fracture, whereas the two femoral tunnels in double bundle ACL reconstruction significantly decreased load to failure. The results support the sparsity of reported peri-ACL reconstruction femur fractures in single femoral tunnel techniques. However, the increased fracture risk in double bundle ACL reconstruction may be a cause for concern and impact patient selection.

     

The posterior horn of the lateral meniscus is a reliable novel landmark for femoral tunnel placement in ACL reconstruction

Purpose

Femoral tunnel placement is essential for good outcome in anterior cruciate ligament (ACL) reconstruction. In the past, several attempts have been made to optimize femoral tunnel placement. It was observed that the posterior horn of the lateral meniscus was always located directly below to the desired femoral ACL tunnel position, when the knee was brought to deep flexion (>?120°). The goal of the present study was to verify the hypothesis that the posterior horn of the lateral meniscus can be used as a landmark for femoral tunnel placement.

Methods

Out of a consecutive series of ACL reconstructions done by a single surgeon, 55 lateral radiographs were evaluated according to the quadrant method by Bernard and Hertel. Additionally, on anterior-posterior radiographs the femoral tunnel angle was determined.

Results

In the present case series the posterior horn of the lateral meniscus could be identified and used as a landmark for femoral tunnel placement in all cases. The mean tunnel depth was 24?±?5.1% and the mean tunnel height was 31.3?±?5.7%. The mean femoral tunnel angle was 41?±?4.9° using the anatomical axis as a reference. Compared to previous cadaver studies the data of the present study were within their anatomical range of the native ACL insertion site.

Conclusion

The suggested technique using the posterior horn of the lateral meniscus as a landmark for femoral tunnel placement showed reproducible results and matches the native ACL insertion site compared to previous cadaveric studies. In particular, non-experienced ACL surgeons will benefit from this apparent landmark and the corresponding easy-to-use ACL reconstruction method.

Level of evidence

IV.

     

Radiographic positions of femoral ACL,AM and PL centres: accuracy of guidelines based on the lateral quadrant method

Purpose

Femoral tunnel positioning is an important factor in anatomical ACL reconstructions. To improve accuracy, lateral radiographic support can be used to determine the correct tunnel location, applying the quadrant method. Piefer et al. (Arthroscopy 28:872–881, 2012) combined various outcomes of eight studies applying this method to one guideline. The studies included in that guideline used various insertion margins, imaging techniques and measurement methods to determine the position of the ACL centres. The question we addressed is whether condensing data from various methods into one guideline, results in a more accurate guideline than the results of one study.

Methods

The accuracy of the Piefer’s guideline was determined and compared to a guideline developed by Luites et al. (2000). For both guidelines, we quantified the mean absolute differences in positions of the actual anatomical centres of the ACL, AM and PL measured on the lateral radiographs of twelve femora with the quadrant method and the positions according to the guidelines.

Results

The accuracy of Piefer’s guidelines was 2.4 mm (ACL), 2.7 mm (AM) and 4.6 mm (PL), resulting in positions significantly different from the actual anatomical centres. Applying Luites’ guidelines for ACL and PL resulted in positions not significantly different from the actual centres. The accuracies were 1.6 mm (ACL) and 2.2 mm (PL and AM), which were significantly different from Piefer for the PL centres, and therefore more accurate.

Conclusions

Condensing the outcomes of multiple studies using various insertion margins, imaging techniques and measurement methods, results in inaccurate guidelines for femoral ACL tunnel positioning at the lateral view.

Clinical relevance

An accurate femoral tunnel positioning for anatomical ACL reconstruction is a key issue. The results of this study demonstrate that averaging of various radiographic guidelines for anatomical femoral ACL tunnel placement in daily practice, can result in inaccurate tunnel positions.

Level of evidence

Diagnostic study, Level 1.

     

Evaluation of the semitendinosus tendon graft shift in the bone tunnel: an experimental study

Purpose

The purpose of this study was to measure the semitendinosus tendon graft shift at the tunnel aperture with graft bending using a simulated femoral bone tunnel.

Methods

Eight semitendinosus tendon grafts were used in this study. The median age of the specimen was 53 years (range 46–63). After stripping excess soft tissue, the semitendinosus tendon was doubled over the loop of the EndoButton CL (Smith and Nephew Inc.). The diameter of the graft was measured using a graft-sizing tube (Smith and Nephew Inc.) and verified to be 7.0 mm. A custom-made aluminium fixture, the size was 40.0 mm³, with 7.0-mm-diameter hole was used as a simulated femoral bone tunnel. The graft was inserted to the tunnel, and EndoButton was positioned to the outside of the tunnel on the fixture. The distal end of the graft was tensioned with 30 N at an angle of 15°, 30°, 45°, 60°, 75° that reproduced the graft bending angle during knee range of motion. The photograph of the tunnel aperture was taken at each graft bending angle using a digital camera, and the graft shift amount in the simulated tunnel was analysed using the computer software (ImageJ).

Results

The amount of the graft shift significantly increased when the graft bending angle was increased (P < 0.05). The biggest shift was observed when the graft bending angle was 75° in all specimens, and the value was 1.10 mm ± 0.12.

Conclusion

The present study suggests that even if the femoral tunnel was created in the centre of the ACL insertion site, the graft shifted within the tunnel in the direction of the tension applied to the graft during knee range of motion. Surgeons may have to consider the graft shift within the bone tunnel as well as the tunnel position in the restoration of the native ACL anatomy.

     

The evaluation of muscle recovery after anatomical single-bundle ACL reconstruction using a quadriceps autograft

Purpose

The purpose of this study was to reveal the degree of muscle recovery and report the clinical results of anatomical single-bundle ACL reconstruction using a quadriceps autograft.

Methods

Twenty subjects undergoing anatomical single-bundle ACL reconstruction using a quadriceps autograft were included in this study. A 5-mm-wide, 8-cm-long graft, involving the entire layer of the quadriceps tendon, was harvested without bone block. The average graft diameter was 8.1 ± 1.4 mm. An initial tension of 30 N was applied. The femoral tunnel was created from the far-medial portal. Each femoral and tibial tunnel was created close to the antero-medial bundle insertion site. For the evaluation of muscle recovery (quadriceps and hamstring), a handheld dynamometer was used. The evaluation of muscle recovery was performed pre-operatively, and at 3, 6, 9, and 12 months after surgery. Muscle recovery data were calculated as a percentage of leg strength in the non-operated leg. Anterior tibial translation (ATT), pivot shift test, and IKDC score were evaluated.

Results

The average quadriceps strength pre-operatively, and at 3, 6, 9, and 12 months after ACL reconstruction was 90.5 ± 19, 67.8 ± 21.4, 84 ± 17.5, and 85.1 ± 12.6 %, respectively. The average hamstring strength pre-operatively, and at 3, 6, 9, and 12 months after ACL reconstruction was 99.5 ± 13.7, 78.7 ± 11.4, 90.5 ± 19, and 96.7 ± 13.8 %, respectively. ATT pre-operatively and at 12 months after surgery was 5.4 ± 1.3 and 1.0 ± 0.8 mm, respectively. No subjects exhibited positive pivot shift after surgery. Within 6 months following surgery, quadriceps hypotrophy was observed in all subjects. However, the hypotrophy had recovered at 12 months following surgery. No subjects complained of donor site pain after surgery.

Conclusion

Anatomical single-bundle ACL reconstruction using a quadriceps autograft resulted in equivalent level of muscle recovery and knee stability when compared with previously reported ACL reconstruction using hamstrings tendon with no donor site complications.

Level of evidence

Case controlled study, Level III.

     

How to avoid collision between PCL and MCL femoral tunnels during a simultaneous reconstruction

Purpose

The purpose of the present study was to assess the risk of femoral tunnel collisions between the medial collateral ligament (MCL) and the posterior cruciate ligament (PCL) tunnels during a simultaneous PCL and MCL reconstruction.

Methods

Fourth generation medium and large synthetic femur bones were used. On each femur, a MCL tunnel and a PCL tunnel were reamed. The MCL tunnel was drilled at 0°, 20° and 40° of axial and coronal angulations. The PCL femoral tunnel was reamed to simulate two different tunnel directions that could be obtained through an inside-out and outside-in technique. Tunnels were filled with epoxy resin augmented with BaSO4, and a multidetector CT examination of each specimen was performed.

Results

High rate of tunnel collision (62.5 %) was found when the MCL femoral tunnel was reamed with a coronal angulation of 0° and 20°. The rate of tunnel collision significantly decreased (0 %) when the MCL tunnel was reamed proximally with a coronal angulation of 40°. No differences were found between the two PCL tunnel directions in terms of tunnel collision.

Conclusion

The results of this study can help surgeons to better direct the femoral MCL tunnel in order to avoid a collision between femoral tunnels during a combined MCL and PCL reconstruction. In order to minimize such potential complications, the MCL tunnel should be created limiting the axial angulation and it should be drilled with a proximal angulation from 20° to 40°, depending on the medial condyle width.

     

Early integration of a bone plug in the femoral tunnel in rectangular tunnel ACL reconstruction with a bone-patellar tendon-bone graft: a prospective computed tomography analysis

Purpose

The purpose of this prospective study was to evaluate how early the bone plug was integrated into the rectangular femoral tunnel after anatomical ACL reconstruction using a bone-patellar tendon-bone (BTB) graft via a rectangular tunnel (RT BTB ACL-R).

Methods

Twenty consecutive patients who had undergone the reconstruction procedure were evaluated by CT scans at 4 and 8 weeks postoperatively. In each scan, 30 slices for multiplanar reconstruction were collected parallel to the long axis of the parallelepiped femoral tunnel and perpendicular to the tendinous plane of the bone plug. Each slice was classified as “complete,” indicating no visible gap between the plug and the tunnel wall or trabecular continuity or “incomplete,” showing a visible gap. Bone plug-tunnel integration was evaluated as “excellent,” “good,” “fair,” or “poor” for >20, 11–20, 5–10, and <4 “complete” slices, respectively.

Results

In this evaluation, 55% of the patients were rated as “excellent” on the first scan, and 80% were “excellent” on the second scan, showing healing over time. The CT values at the anterior interface between the bone plug and the tunnel wall were also measured on both scans. The mean changes in CT value at 8 weeks were significantly lower than those at 4 weeks.

Conclusion

This study shows that bone plug-femoral tunnel integration was almost complete by 8 weeks after surgery using RT BTB ACL-R.

     

Biomechanical and viscoelastic properties of different posterior meniscal root fixation techniques

Purpose

The purpose of the present study was to biomechanically compare three different posterior meniscal root repair techniques. Transtibial fixation of a posterior meniscus root tear (PMRT) combined with an anterior cruciate ligament (ACL) reconstruction via one tunnel only shows similar properties in terms of cyclic loading and load to failure compared with direct anchor fixation.

Methods

Twenty-eight porcine knees were randomly assigned to 4 groups (n = 7 each): (1) native posterior meniscal root, (2) suture anchor repair, (3) refixation via a tibial ACL tunnel in combination with an interference screw fixation of the ACL graft, and (4) refixation via a tibial ACL tunnel in combination with an interference screw fixation of the ACL graft with an additional extracortical button fixation. The four groups underwent cyclic loading followed by a load-to-failure testing. Construct elongation during 1000 cycles, dynamic stiffness, attenuation, maximum force during load-to-failure testing, and failure mode were recorded.

Results

All reconstructions showed a significant lower maximum load (p < 0.0001) compared with the native meniscal root. The elongation for the transtibial fixation via the ACL tunnel without an additional extracortical backup fixation was significantly higher compared with the suture anchor technique (p < 0.0001). The additional use of a backup fixation led to similar results compared with the anchor repair technique.

Conclusion

The transtibial refixation of the meniscal root can be combined with an ACL reconstruction using the same tibial bone tunnel. However, an additional extracortical backup fixation is necessary. This might avoid a slippage of suture material and a failure of meniscus root fixation.

     

Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser

Purpose

This is the first biomechanical study to examine the potential stress riser effect of the tibial tunnel or tunnels after ACL reconstruction surgery. In keeping with literature, the primary hypothesis tested in this study was that the tibial tunnel acts as a stress riser for fracture propagation. Secondary hypotheses were that the stress riser effect increases with the size of the tunnel (8 vs. 10 mm), the orientation of the tunnel [standard (STT) vs. modified transtibial (MTT)], and with the number of tunnels (1 vs. 2).

Methods

Tibial tunnels simulating both single bundle hamstring graft (8 mm) and bone-patellar tendon-bone graft (10 mm) either STT or MTT position, as well as tunnels simulating double bundle (DB) ACL reconstruction (7, 6 mm), were drilled in fourth-generation saw bones. These five experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure on a Materials Testing System to simulate tibial plateau fracture.

Results

There were no statistically significant differences in peak load to failure between any of the groups, including the control group. The fracture occurred through the tibial tunnel in 100 % of the MTT tunnels (8 and 10 mm) and 80 % of the DB tunnels specimens; however, the fractures never (0 %) occurred through the tibial tunnel of the standard tunnels (8 or 10 mm) (P = 0.032).

Conclusions

In the biomechanical model, the tibial tunnel does not appear to be a stress riser for fracture propagation, despite suggestions to the contrary in the literature. Use of a standard, more vertical tunnel decreases the risk of ACL graft compromise in the event of a fracture. This may help to inform surgical decision making on ACL reconstruction technique.

     

Effect of meniscal loss on knee stability after single-bundle anterior cruciate ligament reconstruction

Purpose

The menisci are known to be important secondary constraints to anterior translation of the tibia in the ACL-deficient knee. The effect of meniscal loss on knee stability as measured by the magnitude of the pivot shift following ACL reconstruction is unknown. The objective of this investigation was to determine the effect of meniscectomy on knee stability following two single-bundle ACL reconstruction strategies.

Materials and Methods

A mechanized pivot shift was performed on cadaveric specimens in the ACL-intact and ACL-deficient state. Tibiofemoral translation was recorded using a surgical navigation system. The ACL was reconstructed utilizing a nonanatomic graft (n = 10) extending from the posterolateral tibial footprint to the anteromedial femoral footprint, or an anatomic anteromedial single-bundle graft extending from the anteromedial tibial footprint to the anteromedial femoral footprint (n = 10) and testing repeated. The medial or lateral meniscus was sectioned and the examination repeated. The other meniscus was sectioned and the examination subsequently repeated.

Results

Lateral compartment translation during the pivot shift was significantly reduced following anatomic ACL reconstruction. In the nonanatomic group, lateral compartment translation increased by 9.1 mm (P < 0.001) after unicomparmental meniscectomy and 11.5 mm (P < 0.001) after bicompartmental meniscectomy. In the anatomic reconstruction group, lateral compartment translation increased by 7.6 mm (P < 0.001) after bicompartmental meniscectomy.

Conclusion

With isolated ACL injury, anatomic single-bundle ACL reconstruction controlled the pivot shift during time zero testing. However, significant increases in lateral compartment translation during the pivot shift are seen following bicompartmental meniscectomy. Nonanatomic ACL reconstruction was less effective in controlling the pivot shift at time zero testing, and significant increases in lateral compartment translation during the pivot shift were seen following both unicomparmental and bicompartmental meniscectomy.

     

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.

Level of evidence

Case controlled study, Level III.

     

The remnant preservation technique reduces the amount of bone tunnel enlargement following anterior cruciate ligament reconstruction

Purpose

The aim of the present study was to investigate the correlation between postoperative tunnel enlargement after ACLR and remnant tissue preservation using the hamstring tendon.

Methods

One hundred and ninety-two subjects (male, n = 101; female, n = 91; mean age 27.1) who had undergone double-bundle ACL reconstruction were included in the present study. The patients were divided into two groups: the remnant tissue preservation group (Group R) and the non-remnant tissue preservation group (Group N). Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture for the anteromedial femoral tunnel (FAMT), posterolateral femoral tunnel (FPLT), anteromedial tibial tunnel (TAMT), and posterolateral tibial tunnel (TPLT) was measured. The area at 2 weeks after ACLR was subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. The differences in the outcomes and characteristics of the two groups were evaluated.

Results

Seventy-seven knees were classified into Group R, and 115 knees were classified into Group N. The age, gender, and body mass index did not differ to a statistically significant extent. The percentages of FAMT and TAMT enlargement in Group R were significantly smaller in comparison with Group N (P = 0.003 and P = 0.03, respectively). The percentage of FPLT and TPLT enlargement in the two groups did not differ to a statistically significant extent.

Conclusion

The remnant-preserving technique reduces the amount of bone tunnel enlargement. The present findings indicate the advantages of the remnant-preserving ACLR technique, and therefore the remnant-preserving technique should be recommended.

Level of evidence

II.

     

No clinical differences between anteromedial portal and transtibial technique for femoral tunnel positioning in anterior cruciate ligament reconstruction: a prospective randomized,controlled trial

Purpose

The anteromedial (AMP) portal technique was introduced to position the femoral tunnel in anterior cruciate ligament (ACL) reconstruction to more closely replicate the original ACL footprint compared to the transtibial (TT) approach. Few randomized trials have evaluated differences in these techniques with respect to clinical outcomes. The purpose of this study was to determine if there are any differences in clinical outcome between the AMP and TT approaches.

Methods

This is a single-blinded, prospective, randomized controlled trial. Participants were randomized to undergo ACL reconstruction using the AMP or TT approach. The primary outcome measure was the ACL quality of life (ACL-QOL), and secondary outcomes were the IKDC knee assessment, side-to-side difference in anterior–posterior knee laxity (KT-1000) and tunnel orientation (X-ray findings) at preoperative, 3, 6, 12, and 24 months postoperative. Statistical comparisons were performed using a series of t tests for independent groups with equal variance.

Results

Ninety-six participants were consented and randomized between 2007 and 2011 with eight excluded postrandomization. Mean (SD) preoperative ACL-QOL was 33 (13) for TT and 36 (17) for AMP and improved significantly (p < 0.001) in both groups to 79 (18) and 78 (18) at 24 months postoperative, respectively. The preoperative median IKDC grade for both groups was C and improved similarly in both groups at 24 months (n.s.). There was no side-to-side difference in knee laxity based on KT-1000 measurements with a mean (SD) 1 (3) mm between affected and unaffected limbs in the TT group compared to 1 (3) mm for the AMP group. A significant difference was found in femoral tunnel orientation with the AMP group at 43° (7) and the TT group 58° (8) in the coronal plane (p < 0.001).

Conclusion

No differences in clinical outcome were found when comparing AMP to TT in primary ACL reconstruction using a STG graft. This prospective randomized controlled trial suggests surgeons can use either method without significantly compromising clinical outcome.

Level of evidence

I.

     

Radiographic femoral bicondylar width predicts anterior cruciate ligament insertion site sizes

Purpose

The purpose of this study was to determine whether radiographic femoral bicondylar width predicts intra-operative anterior cruciate ligament (ACL) insertion site sizes.

Methods

Seventy-three consecutive patients (39 males and 34 females; mean age 25.2 years ± 10.2) who underwent anatomic ACL reconstruction were retrospectively reviewed. Femoral condyle width was measured using a pre-operative anteroposterior (AP) radiograph of the operative knee. Lines were drawn through the anatomic axis of the femur, as well as perpendicularly through the condyles. Bicondylar width was measured as the maximum width across both the medial and lateral femoral condyles utilizing this perpendicular line. The ACL insertion site lengths (in the AP direction) of both the tibia and the femur were measured intra-operatively using a commercially available arthroscopic ruler.

Results

The average bicondylar width was significantly smaller for females compared to males (p < 0.05). The average tibial and femoral insertion site sizes were significantly smaller for females compared to males (p < 0.05). Regression analysis predicted tibial (r ² = 0.88) and femoral (r ² = 0.90) insertion site sizes based on femoral bicondylar width measurements.

Conclusion

A simple radiographic measurement of femoral bicondylar width can predict intra-operative tibial and femoral insertion site sizes, which has the potential to assist surgeons in performing individualized ACL reconstruction in cases where MRI scan is unavailable.

Level of evidence

IV.