The effect of anterior cruciate ligament graft rotation on knee biomechanics

Purpose

The purpose of this study was to evaluate the effects on knee biomechanics of rotating the distal end of the bone-patellar tendon graft 90° in anatomic single-bundle (SB) anterior cruciate ligament (ACL) reconstruction with a porcine model.

Methods

Twenty (n = 20) porcine knees were evaluated using a robotic testing system. Two groups and three knee states were compared: (1) intact ACL, (2) deficient ACL and (3) anatomic SB ACL reconstruction with (a) non-rotated graft or (b) rotated graft (anatomic external fibre rotation). Anterior tibial translation (ATT), internal (IR) and external rotation (ER) and the in situ tissue force were measured under an 89-N anterior tibial (AT) load and 4-N m internal and external tibial torques.

Results

A significant difference from the intact ACL was found in ATT at 60° and 90° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There was a significant difference in the in situ force from the intact ACL with AT loading for rotated and non-rotated graft reconstructions at 60° and 90° of knee flexion (p < 0.05). Under IR loading, the in situ force was significantly different from the intact ACL at 30° and 60° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There were no significant differences in ATT, IR, ER and the in situ force between rotated and non-rotated reconstructions.

Conclusion

Graft rotation can be used with anatomic SB ACL reconstruction and not have a deleterious effect on knee anterior and rotational biomechanics. This study has clinical relevance in regard to the use of graft rotation to better reproduce the native ACL fibre orientation in ACL reconstruction.

     

Biomechanical comparison of different graft positions for single-bundle anterior cruciate ligament reconstruction

Purpose

Recent reports have highlighted the importance of an anatomic tunnel placement for anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle ACL reconstruction on knee biomechanics.

Methods

Sixteen fresh-frozen cadaver knees were used. In one group (n = 8), the following techniques were used for knee surgery: (1) anteromedial (AM) bundle reconstruction (AM–AM), (2) posterolateral (PL) bundle reconstruction (PL–PL) and (3) conventional vertical single-bundle reconstruction (PL-high AM). In the other group (n = 8), anatomic mid-position single-bundle reconstruction (MID–MID) was performed. A robotic/universal force-moment sensor system was used to test the knees. An anterior load of 89 N was applied for anterior tibial translation (ATT) at 0°, 15°, 30° and 60° of knee flexion. Subsequently, a combined rotatory load (5 Nm internal rotation and 7 Nm valgus moment) was applied at 0°, 15°, 30° and 45° of knee flexion. The ATT and in situ forces during the application of the external loads were measured.

Results

Compared with the intact ACL, all reconstructed knees had a higher ATT under anterior load at all flexion angles and a lower in situ force during the anterior load at 60° of knee flexion. In the case of combined rotatory loading, the highest ATT was achieved with PL-high AM; the in situ force was most closely restored with MIDMID, and the in situ force was the highest AM–AM at each knee flexion angle.

Conclusion

Among the techniques, AM–AM afforded the highest in situ force and the least ATT.     

Anatomic ACL reconstruction produces greater graft length change during knee range-of-motion than transtibial technique

Purpose

Because distance between the knee ACL femoral and tibial footprint centrums changes during knee range-of-motion, surgeons must understand the effect of ACL socket position on graft length, in order to avoid graft rupture which may occur when tensioning and fixation is performed at the incorrect knee flexion angle. The purpose of this study is to evaluate change in intra-articular length of a reconstructed ACL during knee range-of-motion comparing anatomic versus transtibial techniques.

Methods

After power analysis, seven matched pair cadaveric knees were tested. The ACL was debrided, and femoral and tibial footprint centrums for anatomic versus transtibial techniques were identified and marked. A suture anchor was placed at the femoral centrum and a custom, cannulated suture-centring device at the tibial centrum, and excursion of the suture, representing length change of an ACL graft during knee range-of-motion, was measured in millimeters and recorded using a digital transducer.

Results

Mean increase in length as the knee was ranged 120°–0° (full extension) was 4.5 mm (±2.0 mm) for transtibial versus 6.7 mm (±0.9 mm) for anatomic ACL technique. A significant difference in length change occurs during knee range-of-motion both within groups and between the two groups.

Conclusions

Change in length of the ACL intra-articular distance during knee range-of-motion is greater for anatomic socket position compared to transtibial position. Surgeons performing anatomic single-bundle ACL reconstruction may tension and fix grafts with the knee in full extension to minimize risk of graft stretch or rupture or knee capture during full extension. This technique may also result in knee anterior–posterior laxity in knee flexion.     

Anatomic double-bundle ACL reconstruction restricts knee extension in knees with hyperextension

Purpose

Double-bundle ACL reconstruction has been demonstrated to be at least as effective as single-bundle reconstruction in terms of restoring knee rotational and translational stability. Until now, the influence on knees with hyperextension has not been evaluated. It was the purpose of this study to evaluate whether double-bundle ACL reconstruction restricts extension in hyperextendable knees.

Methods

Hamstring tendon reconstructions of 10 human cadaveric knees with the ability of hyperextension (age: 48 ± 14 years) were performed as single bundle (SB) on one side and double bundle (DB) on the other side. A surgical navigation system (BrainLab, Germany) was used to assess the kinematics of each knee at the intact and reconstructed state. A difference with regard to the anterior-to-posterior translation (AP) and rotational stability at 30° of knee flexion, 90° of flexion and the hyperextension capability of each specimen was analysed.

Results

The difference in AP translation before and after the reconstruction was not significantly different in 30° and 90° of flexion (n.s). Both single- and double-bundle reconstructions restored the preoperative kinematics at 30° and 90° of knee flexion (n.s). The knee extension was 4° ± 1.8° with the intact ACL and 4° ± 1.7° after reconstruction in the SB group (n.s). The knee extension was 5° of hyperextension ± 1.1° with the intact ACL and 0° ± 0.4° after reconstruction in the DB group; the limitation of the extension was significantly larger in this group (p = 0.013).

Conclusion

Both single- and double-bundle ACL reconstruction techniques are capable of restoring knee anteroposterior and rotational stability. Double-bundle reconstructions significantly reduce knee extension in knees with hyperextension capability. Care must be taken when using double-bundle techniques in patients with knee hyperextension as this procedure may limit the knee extension after double-bundle ACL reconstruction.     

Roles of ACL remnants in knee stability

Purpose

This study evaluated knee laxity in anterior tibial translation and rotation following removal of anterior cruciate ligament (ACL) remnants using a computer navigation system.

Methods

This prospective study included 50 knees undergoing primary ACL reconstruction using a navigation system. ACL remnants were classified into four morphologic types: Type 1, bridging between the roof of the intercondylar notch and tibia; Type 2, bridging between the posterior cruciate ligament and tibia; Type 3, bridging between the anatomical insertions of the ACL on the lateral wall of the femoral condyle and the tibia; and Type 4, no bridging of ACL remnants. Anterior tibial translation and rotatory laxity were measured before and after remnant resection using a navigation system at 30°, 60°, and 90° of knee flexion. The amount of change in anterior tibial translation and rotatory laxity of each type was compared among the types.

Results

The different morphologic types of ACL remnants were as follows: Type 1, 15 knees; Type 2, 9 knees; Type 3, 6 knees; and Type 4, 20 knees. The amount of change in anterior tibial translation and rotatory laxity at 30° knee flexion in Type 3 was significantly larger than in the other types. There were no significant differences in either tibial translation or rotatory laxity at 60° and 90° knee flexion among the types.

Conclusions

In Type 3, ACL remnants contributed to anteroposterior and rotatory knee laxity evaluated at 30° knee flexion. The bridging point of the remnants is important to knee laxity. The Type 3 remnant should be preserved as much as possible when ACL reconstruction surgery is performed.

Level of evidence

Prognostic study, Level II.     

Prospective randomized comparison of anatomic single- and double-bundle anterior cruciate ligament reconstruction

Purpose

To determine if anatomic double-bundle anterior cruciate ligament (ACL) reconstruction is superior to anatomic single-bundle reconstruction in restoring the stabilities and functions of the knee joint.

Methods

A prospective randomized clinical study was done to compare the results of 32 cases of anatomic single-bundle ACL reconstruction and 34 cases of anatomic double-bundle ACL reconstruction with average follow-up of 16.3 ± 3.1 months. Tunnel placements of all the cases were measured on 3D CT. Clinical results were collected after reconstruction; graft’s appearance, meniscus status and cartilage state under arthroscopy were compared and analysed too.

Results

Tunnel placements, confirmed with 3D CT, were in the anatomic positions as described in literature both in SB and DB group. No differences were found between SB and DB groups in clinical outcome scores, pivot shift test and KT 1000 measurements (average side-to-side difference for anterior tibial translation was 0.7 mm in SB group and 1.0 mm in DB group). More than 70 % of the single-bundle graft and AM bundle graft in DB group appeared excellent, but only 44.1 % of PL bundle grafts in DB group were excellent and 11.8 % were in poor state. No new menisci tear was found either in SB or DB group, however, in DB group cartilage damages in medial patella-femoral joint occurred in 38.2 % cases. This rate was significantly higher than in the SB group which is only 9.3 %.

Conclusion

Both single- and double-bundle anatomic ACL reconstruction can restore the knee’s stability and functions very well. However, more incidences of poor PL status and medial patellar-femoral cartilage damage may occur in double-bundle ACL reconstruction.

Level of evidence

Randomized controlled trial, Level 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.

     

Coronal tibial anteromedial tunnel location has minimal effect on knee biomechanics

Purpose

Studies have found anatomic variation in the coronal position of the insertion site of anteromedial (AM) bundle of the anterior cruciate ligament (ACL) on the tibia, which can lead to questions about tunnel placement during ACL reconstruction. The purpose of this study was to determine how mediolateral placement of the tibial AM graft tunnel in double-bundle ACL reconstructions affects knee biomechanics.

Methods

Two different types of double-bundle ACL reconstructions were performed. The AM tibial tunnel was placed at either the medial or lateral portion of tibial AM footprint. Nine cadaveric knees were tested with the robotic/universal force-moment sensor system with the use of (1) an 89.0-N anterior tibial load at full extension (FE), 30°, 60° and 90° of knee flexion and (2) a combined 7.0-Nm valgus torque and 5.0-Nm internal tibial rotation torque at FE, 15°, 30°and 45° of knee flexion.

Results

Both medial (2.6?±?1.2 mm) and lateral (1.6?±?0.9 mm) double-bundle reconstructions reduced the anterior tibial translation (ATT) to less than the intact value (3.9?±?0.7 mm) at FE. At all other flexion angles, there was no significant different in ATT between the intact knee and the reconstructions. At FE, the ATT for the medial AM reconstruction was different from that of the lateral AM construction and closer to the intact ACL value.

Conclusion

The coronal tibial placement of the AM tunnel had only a slight effect on knee biomechanics. In patients with differing AM bundle coronal positions, the AM tibial tunnel can be placed anatomically at the native insertion site.

     

Tibial internal rotation is affected by lateral laxity in cruciate-retaining total knee arthroplasty: an intraoperative kinematic study using a navigation system and offset-type tensor

Purpose

The purpose of this study was to test the hypothesis that intraoperative soft-tissue balance assessed by an offset-type tensor influences post-operative knee kinematics after cruciate-retaining (CR) total knee arthroplasty (TKA).

Methods

The influence of intraoperative soft-tissue balance on knee kinematics in CR-TKA was retrospectively analysed in 30 patients. Intraoperative soft-tissue balance parameters such as varus angle (varus ligament balance), joint component gap (centre gap), and medial and lateral compartment gaps were measured in the navigation system while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Tibial internal rotation and tibial anterior translation were measured as the differences between the values at 60° and 120° of flexion using the navigation system. Correlations between the soft-tissue parameters and post-operative knee kinematics were analysed.

Results

The varus ligament balance was positively correlated with tibial internal rotation at 60° and 90° of flexion (R = 0.54, P < 0.05; R = 0.60, P < 0.01, respectively). Furthermore, the joint component gap was positively correlated with tibial internal rotation at 90° of flexion (R = 0.44, P < 0.05), and the lateral compartment gap was positively correlated with tibial internal rotation at 60°, 90°, and 120° of knee flexion.

Conclusions

The intraoperative varus ligament balance and joint component gap values were factors that predicted post-operative knee kinematics after CR-TKA. Lateral laxity at mid-to-deep knee flexion plays a significant role in tibial internal rotation.

Level of evidence

III.     

Effect of tunnel position for anatomic single-bundle ACL reconstruction on knee biomechanics in a porcine model

Attention has been focused on the importance of anatomical tunnel placement in anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle (SB) ACL reconstruction on knee kinematics. Ten porcine knees were used for the following reconstruction techniques: three different anatomic SB [AM–AM (antero-medial), PL–PL (postero-lateral), and MID–MID] (n = 5 for each group), conventional SB (PL–high AM) (n = 5), and anatomic double-bundle (DB) (n = 5). Using a robotic/universal force–moment sensor testing system, an 89 N anterior load (simulated KT1000 test) at 30, 60, and 90° of knee flexion and a combined internal rotation (4 N m) and valgus (7 N m) moment (simulated pivot-shift test) at 30 and 60° were applied. Anterior tibial translation (ATT) (mm) and in situ forces (N) of reconstructed grafts were calculated. During simulated KT1000 test at 60° of knee flexion, the PL–PL had significantly lower in situ force than the intact ACL (P < 0.01). In situ force of the MID–MID was higher than other SB reconstructions (at 30°: 94.8 ± 2.5 N; at 60°: 85.2 ± 5.3 N; and 90°: 66.0 ± 8.7 N). At 30° of knee flexion, the PL–high AM had the lowest in situ values (67.1 ± 19.3 N). At 60 and 90° of knee flexion the PL–PL had the lowest in situ values (at 60°: 60.8 ± 19.9 N; 90°: 38.4 ± 19.2 N). The MID–MID and DB had no significant in situ force differences at 30 and 60° of knee flexion. During simulated pivot-shift test at 60° of knee flexion, the PL–PL and PL–high AM reconstructions had a significant lower in situ force than the intact ACL (P < 0.01). During simulated KT1000 test at 30, 60, and 90° of knee flexion, the PL–PL and PL–high AM had significantly lower ATT than the intact ACL (P < 0.01). During simulated KT1000 test at 60 and 90°, the MID–MID, AM–AM, and DB had significantly lower ATT than the ACL deficient knee (P < 0.01). During simulated KT1000 test at 90°, every reconstructed knee had significantly higher ATT than the intact knee (P < 0.01). In conclusion, the MID–MID position provided the best stability among all anatomic SB reconstructions and more closely restored normal knee kinematics.     

Restoring tibiofemoral alignment during ACL reconstruction results in better knee biomechanics

Purpose

Anterior cruciate ligament (ACL) reconstruction (ACLR) aims to restore normal knee joint function, stability and biomechanics and in the long term avoid joint degeneration. The purpose of this study is to present the anatomic single bundle (SB) ACLR that emphasizes intraoperative correction of tibiofemoral subluxation that occurs after ACL injury. It was hypothesized that this technique leads to optimal outcomes and better restoration of pathological tibiofemoral joint movement that results from ACL deficiency (ACLD).

Methods

Thirteen men with unilateral ACLD were prospectively evaluated before and at a mean follow-up of 14.9 (SD?=?1.8) months after anatomic SB ACLR with bone patellar tendon bone autograft. The anatomic ACLR replicated the native ACL attachment site anatomy and graft orientation. Emphasis was placed on intraoperative correction of tibiofemoral subluxation by reducing anterior tibial translation (ATT) and internal tibial rotation. Function was measured with IKDC, Lysholm and the Tegner activity scale, ATT was measured with the KT-1000 arthrometer and tibial rotation (TR) kinematics were measured with 3Dmotion analysis during a high-demand pivoting task.

Results

The results showed significantly higher TR of the ACL-deficient knee when compared to the intact knee prior to surgery (12.2° ± 3.7° and 10.7° ± 2.6° respectively, P?=?0.014). Postoperatively, the ACLR knee showed significantly lower TR as compared to the ACL-deficient knee (9.6°±3.1°, P?=?0.001) but no difference as compared to the control knee (n.s.). All functional scores were significantly improved and ATT was restored within normal values (P?<?0.001).

Conclusions

Intraoperative correction of tibiofemoral subluxation that results after ACL injury is an important step during anatomic SB ACLR. The intraoperative correction of tibiofemoral subluxation along with the replication of native ACL anatomy results in restoration of rotational kinematics of ACLD patients to normal levels that are comparable to the control knee. These results indicate that the reestablishment of tibiofemoral alignment during ACLR may be an important step that facilitates normal knee kinematics postoperatively.

Level of evidence

Level II, prospective cohort study.

     

Anatomic and non-anatomic anterior cruciate ligament posterolateral bundle augmentation affects graft function

Purpose

The purpose of this study is to compare knee laxity and graft function (tissue force) between anatomic and non-anatomic posterolateral (PL) bundle augmentation.

Methods

Twelve (n = 12) fresh-frozen mature, unpaired porcine knees were tested using a robotic testing system. Four knee states were compared: (a) intact anterior cruciate ligament (ACL), (b) deficient PL and intermediate bundles, (c) anatomic PL augmentation, and (d) non-anatomic PL augmentation. Anterior tibial translation (ATT), internal rotation (IR) and external rotation (ER), and the in situ tissue force were measured under an 89.0-N anterior tibial load and 4.0-N m internal and external tibial torques.

Results

Both anatomic and non-anatomic PL augmentation restored the ER, IR, and ATT of the intact knee at all knee flexion angles (n.s.). Both anatomic and non-anatomic PL augmentation restored the in situ tissue force of the ACL during ER and IR loading and ATT loading at all knee flexion angles except at 60° of knee flexion, where the non-anatomic PL augmentation did not restore the in situ tissue force of the ACL during external rotation loading and the anatomic PL augmentation did not restore the in situ tissue force of the ACL during IR loading. Furthermore, there were no differences in ATT, IR, ER, and in situ tissue force under anterior tibial loading, IR and ER loading between the two reconstruction groups.

Conclusion

There were no significant differences between anatomic and non-anatomic PL augmentation using the porcine knee model.

     

The effect of posterior tibial slope on knee flexion in posterior-stabilized total knee arthroplasty

Purpose

To evaluate and quantify the effect of the tibial slope on the postoperative maximal knee flexion and stability in the posterior-stabilized total knee arthroplasty (TKA).

Methods

Fifty-six patients (65 knees) who had undergone TKA with the posterior-stabilized prostheses were divided into the following 3 groups according to the measured tibial slopes: Group 1: ≤4°, Group 2: 4°–7° and Group 3: >7°. The preoperative range of the motion, the change in the posterior condylar offset, the elevation of the joint line, the postoperative tibiofemoral angle and the preoperative and postoperative Hospital for Special Surgery (HSS) scores were recorded. The tibial anteroposterior translation was measured using the Kneelax 3 Arthrometer at both the 30° and the 90° flexion angles.

Results

The mean values of the postoperative maximal knee flexion were 101° (SD 5), 106° (SD 5) and 113° (SD 9) in Groups 1, 2 and 3, respectively. A significant difference was found in the postoperative maximal flexion between the 3 groups (P < 0.001). However, no significant differences were found between the 3 groups in the postoperative HSS scores, the changes in the posterior condylar offset, the elevation of the joint line or the tibial anteroposterior translation at either the 30° or the 90° flexion angles. A 1° increase in the tibial slope resulted in a 1.8° flexion increment (r = 1.8, R ² = 0.463, P < 0.001).

Conclusion

An increase in the posterior tibial slope can significantly increase the postoperative maximal knee flexion. The tibial slope with an appropriate flexion and extension gap balance during the operation does not affect the joint stability.

Level of evidence

Retrospective comparative study, Level III.     

Double-bundle reconstruction results in superior clinical outcome than single-bundle reconstruction

Purpose

To compare the short- and long-term clinical outcomes of the double-bundle (DB) anterior cruciate ligament (ACL) reconstruction with those of single-bundle (SB) ACL reconstruction.

Methods

An electronic search of the database PubMed (1966–September 2011), EMBASE (1984–September 2011), and Cochrane Controlled Trials Register (CENTRAL; 3rd Quarter, 2011) was undertaken to identify relevant studies. Main clinical outcomes were knee stability measurements including KT-1000 arthrometer measurement, Pivot shift test, and Lachman test, and clinical outcome measurements including International Knee Documentation Committee (IKDC), Lysholm knee score, Tegner activity score, and complications.

Results

Eighteen studies were finally included in this meta-analysis, which were all classified as high risk of bias according to the Collaboration’s recommended tool. It is seen that compared to SB ACL reconstruction, DB ACL reconstruction results in a KT-1000 arthrometer outcome 0.63 and 1.00 mm closer to the normal knee in a short- and long-term follow-up, respectively. Our results also reveal that DB-treated patients have a significantly higher negative rate of the pivot shift test (p < 0.00001 and = 0.006 in a short- and long-term follow-up, respectively) and Lachman test (n.s. and p < 0.0001 in a short- and long-term follow-up, respectively) compared to SB-treated patients. As for the clinical outcome measurements, a significant difference is found between SB versus DB ACL reconstruction regarding the IKDC (p = 0.006 and < 0.0001 in a short- and long-term follow-up, respectively) and complications (p = 0.03), while there is no significant difference between the two groups regarding Lysholm knee score (n.s.) and Tegner activity score (n.s.).

Conclusion

Overall, double-bundle ACL reconstruction yields better clinical outcomes when compared to single-bundle ACL reconstruction.

Levels of evidence

II.     

A comparison of dynamic rotational knee instability between anatomic single-bundle and over-the-top anterior cruciate ligament reconstruction using triaxial accelerometry

Purpose

Recently, single-bundle (SB) anterior cruciate ligament (ACL) reconstruction has been advanced by the anatomic concept, but the biomechanical outcome of the anatomic method has not been fully investigated, especially for rotational instability. Anatomic SB and the single over-the-top procedures are the treatment of choice for primary cases and revision or skeletally immature cases, respectively. The purpose of this study was to investigate the dynamic rotational instability of anatomic SB and over-the-top reconstruction during a pivot shift test using triaxial accelerometry.

Methods

Eight fresh frozen human cadaveric knees were used in this study. Rotational instability measurement was conducted during a pivot shift test by the use of a triaxial accelerometer attached to the tibia. The tests were performed in the ACL-intact, ACL-deficient and ACL-reconstructed knees with two different procedures (anatomic SB and over-the-top). The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between four different knee states.

Results

The overall magnitude of acceleration was significantly different (P < 0.01) between the ACL-intact knees and the ACL-deficient knees. Both anatomic SB and over-the-top ACL reconstruction significantly reduced the overall magnitude of acceleration compared to the ACL-deficient knees, but still had larger accelerations compared to the ACL-intact knees. There was no significant difference for the overall magnitude of acceleration between anatomic SB and over-the-top reconstruction procedure.

Conclusion

Over-the-top reconstruction provides comparable result to anatomic SB reconstruction in terms of controlling the dynamic rotational stability. Over-the-top reconstruction might be one of the options for revision cases and in skeletally immature patients.     

Anatomic single- versus double-bundle ACL reconstruction: a meta-analysis

Purpose

To determine whether anatomic double-bundle anterior cruciate ligament (ACL) reconstruction compared to anatomic single-bundle ACL reconstruction more effectively restored antero–posterior (A–P) laxity, rotatory laxity and reduced frequency of graft rupture. Our hypothesis was that anatomic double-bundle ACL reconstruction results in superior rotational knee laxity and fewer graft ruptures due to its double-bundle tension pattern, compared with anatomic single-bundle ACL reconstruction.

Methods

An electronic search was performed using the PubMed, EMBASE and Cochrane Library databases. All therapeutic trials written in English reporting knee kinematic outcomes and graft rupture rates of primary anatomic double- versus single-bundle ACL reconstruction were included. Only clinical studies of levels I–II evidence were included. Data regarding kinematic tests were extracted and included pivot-shift test, Lachman test, anterior drawer test, KT-1000 measurements, A–P laxity measures using navigation and total internal–external (IRER) laxity measured using navigation, as well as graft failure frequency.

Results

A total of 7,154 studies were identified of which 15 papers (8 randomized controlled trials and 7 prospective cohort studies, n = 970 patients) met the eligibility criteria. Anatomic ACL double-bundle reconstruction demonstrated less anterior laxity using KT-1000 arthrometer with a standard mean difference (SMD) = 0.36 (95 % CI 0.214–0.513, p < 0.001) and less A–P laxity measured with navigation (SMD = 0.29 95 % CI 0.01–0.565, p = 0.042). Anatomic double-bundle ACL reconstruction did not lead to significant improvements in pivot-shift test, Lachman test, anterior drawer test, total IRER or graft failure rates compared to anatomic single-bundle ACL reconstruction.

Conclusion

Anatomic double-bundle ACL reconstruction is superior to anatomic single-bundle reconstruction in terms of restoration of knee kinematics, primarily A–P laxity. Whether these improvements of laxity result in long-term improvement of clinical meaningful outcomes remains uncertain.

Level of evidence

II.     

Improvement in the medial meniscus posterior shift following anterior cruciate ligament reconstruction

Purpose

Anterior cruciate ligament (ACL) reconstruction can reduce the risk of developing osteoarthritic knees. The goals of ACL reconstruction are to restore knee stability and reduce post-traumatic meniscal tears and cartilage degradation. A chronic ACL insufficiency frequently results in medial meniscus (MM) injury at the posterior segment. How ACL reconstruction can reduce the deformation of the MM posterior segment remains unclear. In this study, we evaluated the form of the MM posterior segment and anterior tibial translation before and after ACL reconstruction using open magnetic resonance imaging (MRI).

Methods

Seventeen patients who underwent ACL reconstructions without MM injuries were included in this study. MM deformation was evaluated using open MRI before surgery and 3 months after surgery. We measured medial meniscal length (MML), medial meniscal height (MMH), medial meniscal posterior body width (MPBW), MM–femoral condyle contact width (M-FCW) and posterior tibiofemoral distance (PTFD) at knee flexion angles of 10° and 90°.

Results

There were no significant pre- and postoperative differences during a flexion angle of 10°. At a flexion angle of 90°, MML decreased from 43.7 ± 4.5 to 41.4 ± 4.5 mm (P < 0.001), MMH from 7.5 ± 1.4 to 6.9 ± 1.4 mm (P = 0.006), MPBW from 13.1 ± 2.0 to 12.2 ± 1.9 mm (P < 0.001) and M-FCW from 10.0 ± 1.5 to 8.5 ± 1.5 mm (P < 0.001) after ACL reconstruction. The PTFD increased from 2.1 ± 2.8 to 2.7 ± 2.4 mm after ACL reconstruction (P = 0.015).

Conclusions

ACL reconstruction affects the contact pattern between the MM posterior segment and medial femoral condyle and can reduce the deformation of the MM posterior segment in the knee-flexed position by reducing abnormal anterior tibial translation. It possibly prevents secondary injury to the MM posterior segment and cartilage that progresses to knee osteoarthritis.

Level of evidence

IV.

     

Can a tibial tunnel in ACL surgery be placed anatomically without impinging on the femoral notch? A risk factor analysis

Purpose

To analyze anatomical risk factors and surgical technique dependent variables, which determine the risk for femoral notch impingement in anatomically correct placed tibial tunnels for anterior cruciate ligament (ACL) surgery.

Methods

Twenty fresh frozen adult human knee specimens under the age of 65 years were used. Digital templates mimicking a tibial tunnel aperture at the tibia plateau were designed for different tibial tunnel diameters and different drill-guide angles. The centres of these templates were placed over the geometric centre of the native tibial ACL footprint. The distances between the anterior borders of the templates and the anterior borders of the footprints (graft free zone) were measured and compared. Furthermore, anatomic risk factors for femoral notch impingement were determined.

Results

The graft free zone was statistically significantly longer for larger drill-guide angles compared to smaller drill-guide angles (p < 0.00001). Furthermore, 8 mm diameter tibial tunnels had a statistically significant larger graft free zone compared to 10-mm-diameter tibial tunnels (p < 0.00001). For the 10 mm diameter tibial tunnels with drill-guide angle of 45°, 9 out of 20 knees (45 %) were “at risk” for notching and 4 out of 20 knees (20 %) had “definite” notching. For 10-mm tunnels with drill-guide angle of 45°, a risk for notching was associated with smaller tibial ACL footprint (p < 0.05).

Conclusion

If a perfect centrally positioned tibial tunnel is drilled, a real risk for femoral notch impingement exists depending on the size of the tibial ACL footprint and surgery-related factors. Therefore, in anatomical tibial tunnel placement in single bundle ACL reconstruction surgery, particular attention should be paid to size of the tunnel and drill-guide angle to minimize the risk of femoral notch impingement.     

Association between varus alignment and post-traumatic osteoarthritis after anterior cruciate ligament injury

Purpose

To investigate the association between varus alignment and post-traumatic osteoarthritis (OA) after an anterior cruciate ligament (ACL) injury.

Methods

One hundred subjects with an acute complete ACL tear were followed for 15 years. Anterior–posterior radiographs of the tibiofemoral joint were obtained with a knee flexion of 20°, and the patellofemoral joint was examined with skyline view at 50° knee flexion. Joint space narrowing and osteophytes were graded in the tibiofemoral and patellofemoral joints in the injured (ACL) and uninjured knee according to the radiographic atlas of the Osteoarthritis Research Society International. The alignment of the uninjured, contralateral knee was measured at follow-up, using full-limb radiographs of leg with the knee in full extension. Alignment was expressed as the hip-knee-ankle (HKA) angle. Alignment was defined as valgus (HKA ≤178°), neutral (179°–181°) or varus (≥182°).

Results

Data from 68 subjects were included in the analysis. Varus alignment of the uninjured knee at follow-up appeared to be associated with OA of the injured knee 15 years after an ACL injury (odds ratio (95 % confidence interval) 3.9 (1.0–15.8, p = 0.052)).

Conclusions

Varus alignment of the uninjured knee at follow-up may be associated with OA of the injured knee 15 years after an ACL injury.

Level of evidence

II.     

The influence of the tibial slope on intra-operative soft tissue balance in cruciate-retaining and posterior-stabilized total knee arthroplasty

Purpose

This study aims to make clear the influence of the tibial slope on intra-operative soft tissue balance measurements using a tensor in cruciate-retaining and posterior-stabilized total knee arthroplasty (TKA).

Methods

Forty patients with osteoarthritis of the knee received TKAs (20 cruciate-retaining TKAs and 20 posterior-stabilized TKA). Soft tissue balance was measured using an offset type tensor at 0, 10, 45, 90, 135 degrees of knee flexion. The tibial slopes were measured by post-operative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed.

Results

Joint component gap at 90° (R = 0.537, p < 0.01) and 135° (R = 0.463, p < 0.05) of flexion and joint component gap change value of 90–0° (R = 0.433, p < 0.05) showed positive correlations with tibial slope in posterior-stabilized TKA. There was no relationship between the tibial slope and the value of soft tissue balances in cruciate-retaining TKA.

Conclusions

In the present study, we confirmed that increasing the tibial slope resulted in a larger flexion gap compared to extension gap in posterior-stabilized TKA. Surgeons should be aware that increasing the tibial slope is one factor responsible for widening the flexion–extension gap difference in posterior-stabilized TKA.

Level of evidence

III.