Superior graft maturation after anatomical double-bundle anterior cruciate ligament reconstruction using the transtibial drilling technique compared to the transportal technique

No Difference in Graft Signal Intensity on MRI or Clinical Outcome Between Anterior Cruciate Ligament Reconstruction With and Without Suture Augmentation

PURPOSE

To evaluate the safety of anterior cruciate ligament reconstruction (ACLR) with suture augmentation (SA) through clinical evaluations, monitoring of complications, and evaluation of early graft remodeling using magnetic resonance imaging (MRI).

METHODS

Data of participants who underwent anatomic double-bundle ACLR using hamstring tendon autografts, with a minimum 2-year follow-up, were retrospectively reviewed. Participants undergoing ACLR with SA were propensity-matched with those without SA. Postoperative clinical evaluations, including Lysholm and Tegner activity scores, International Knee Documentation Committee (IKDC) evaluation scores, KT-1000 side-to-side difference for knee stability at a 2-year follow-up, and complications, were recorded. The minimal clinically important difference (MCID) was calculated for IKDC scores. The anteromedial bundle graft was categorized into distal, middle, and proximal regions on the 6-month and 1-year postoperative MRI. The signal-to-noise quotient (SNQ) of each region of interest was calculated to evaluate the graft signal intensity, which was compared between the two groups using Welch's t-test.

RESULTS

Fifty-three participants were included in each group. No significant differences were observed between the non-SA and SA groups in the Lysholm scores (96.6 ± 6.2; 95.3 ± 5.8, P = 0.25), Tegner activity scores (4.8 ± 1.4; 5.0 ± 1.3, P = 0.49), IKDC scores (90.4 ± 10.8; 87.1 ± 12.9, P = 0.15), percentage of patients meeting the MCID (94.3%; 83.0%, P = 0.12), or postoperative KT-1000 side-to-side difference (0.9 ±1.2; 0.7 ± 1.8 mm, P = 0.56). One (1.8%) and two (3.7%) cases of re-tears occurred in the non-SA and SA groups, respectively; no other complications occurred. The postoperative SNQ measurements revealed no significant differences in signal changes in all regions of the grafts between the two groups.

CONCLUSIONS

This study confirmed no difference in graft signal intensity on MRI or clinical outcome between ACLR with and without SA at the 2-year follow-up.

LEVEL OF EVIDENCE

Level III, retrospective, comparative study.

Transtibial Versus Anteromedial Portal Technique for Femoral Tunnel Drilling in Primary Single-Bundle Anterior Cruciate Ligament Reconstruction: A Meta-analysis of Level 1 and 2 Evidence of Clinical, Revision, and Radiological Outcomes

BACKGROUND

Although numerous clinical studies have compared transtibial (TT) and anteromedial portal (AMP) drilling of femoral tunnels during anterior cruciate ligament reconstruction (ACLR), there is no high-quality, evidence-based consensus regarding which technique affords the best outcome.

HYPOTHESIS

There would be no difference between the TT and AMP techniques in terms of knee stability, patient-reported outcomes, incidence of revision, and radiological results.

STUDY DESIGN

Meta-analysis; Level of evidence, 2.

METHODS

The PubMed and EMBASE databases were searched from inception to February 1, 2021. Level 1 and 2 clinical trials that compared TT and AM techniques were included. Data were meta-analyzed for the outcome measures of knee stability, patient-reported functional outcomes, incidence of revision, and radiological results. Dichotomous variables were presented as odds ratios (ORs), and continuous variables were presented as mean differences (MDs) and standard mean differences (SMDs).

RESULTS

The meta-analysis included 18 clinical studies, level of evidence 1 or 2, that involved 53,888 patients. Pooled data showed that the AMP group had a lower side-to-side difference (SMD, 0.22; 95% CI, 0.06 to 0.39; P = .009), a lower incidence of pivot-shift phenomenon (OR, 3.69; 95% CI, 1.26 to 10.79; P = .02), and a higher postoperative Lysholm score (SMD, -0.26; 95% CI, -0.44 to -0.08; P = .005) than the TT group. However, no statistically significant differences were seen in other outcomes, including subjective International Knee Documentation Committee scores (SMD, -0.11; 95% CI, -0.30 to 0.09; P = .30) or grades (OR, 0.93; 95% CI, 0.35 to 2.49; P = .89), postoperative activity level (MD, -0.14; 95% CI, -0.42 to 0.15; P = .35), and incidence of revision ACLR (OR, 1.04; 95% CI, 0.93 to 1.16; P = .45). The TT technique was more likely to create longer (SMD, 1.05; 95% CI, 0.05 to 2.06; P = .04) and more oblique (SMD, 0.81; 95% CI, 0.51 to 1.11; P < .001) femoral tunnels than the AMP technique, and a higher height ratio of the aperture position was detected with the TT technique (SMD, -3.51; 95% CI, -5.54 to -1.49; P < .001).

CONCLUSION

The AMP technique for ACLR may be more likely to produce better knee stability and improved clinical outcomes than the TT technique, but no difference was found in the incidence of revision between the 2 groups.

The Hybrid Transtibial Technique for Femoral Tunnel Drilling in Anterior Cruciate Ligament Reconstruction: A Finite Element Analysis Model of Graft Bending Angles and Peak Graft Stresses in Comparison With Transtibial and Anteromedial Portal Techniques

PURPOSE

The purpose of this finite element analysis was to compare femoral tunnel length; anterior cruciate ligament reconstruction graft bending angle; and peak graft stress, contact force, and contact area created by the transtibial, anteromedial portal (AMP), and hybrid transtibial techniques.

METHODS

Finite element analysis modeling was used to examine anterior cruciate ligament reconstruction models based on transtibial, AMP, and hybrid transtibial femoral tunnel drilling techniques. An evaluation of femoral tunnel length, graft bending angle, peak graft stress, contact force, and contact area was done in comparison of these techniques.

RESULTS

The femoral tunnel created with the hybrid transtibial technique was 45.3 mm, which was 13.3% longer than that achieved with the AMP technique but 15.2% shorter than that with the transtibial technique. The femoral graft bending angle with the hybrid transtibial technique (105°) was less acute than that with the AMP technique (102°), but more acute than that with the transtibial technique (109°). At 11° knee flexion, the hybrid transtibial technique had 22% less femoral contact force, 21% less tibial contact force, 21% less graft tension than the AMP technique. Yet, the hybrid transtibial technique had 41% greater femoral contact force, 39% greater tibial contact force, 33% greater graft tension, and 6% greater graft von Mises stress than the transtibial technique. A similar trend was found for the anterior knee drawer test. At both 6-mm anterior tibial displacement and 11° knee flexion, the hybrid transtibial and AMP techniques had at least 51% more femoral contact area than the transtibial technique.

CONCLUSION

This finite element analysis highlights that the hybrid transtibial technique is a true hybrid between the AMP and transtibial techniques for femoral tunnel drilling regarding femoral tunnel length, graft bending angle, and peak graft stress.

Effect of Anterolateral Structure Augmentation on Graft Maturity After Anterior Cruciate Ligament Reconstruction: A Clinical and MRI Follow-up of 2 Years

BACKGROUND

Anterolateral structure augmentation (ALSA) has been applied to prevent residual rotatory instability and lower clinical failure rates after anterior cruciate ligament (ACL) reconstruction (ACLR); however, the effect of combined ALSA on the maturity of ACL grafts remains unknown.

PURPOSE

To evaluate the graft maturity and patient-reported outcomes in patients who underwent double-bundle ACLR with or without ALSA.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 92 patients who underwent double-bundle ACLR between January 2016 and July 2019 were included in the present study-44 patients with isolated ACLR (ACLR group) and 48 patients with combined ACLR and ALSA (ALSA group). Demographic characteristics, intraoperative findings, and patient-reported outcomes were prospectively collected. On postoperative magnetic resonance imaging at the 2-year follow-up, the signal-to-noise quotient (SNQ) values were separately calculated for 6 sections of the ACL graft, including the femoral intratunnel graft (FTG), intra-articular graft (IAG), and tibial intratunnel graft (TTG) of the anteromedial bundle (AMB) and the posterolateral bundle (PLB). Superior graft maturity was usually indicated by lower SNQ values.

RESULTS

The rates of return to preinjury sports were 47.9% and 27.3% in the ALSA and ACLR groups, respectively (difference, 20.6% [95% CI, 1.3%-40%]; P = .042). The AMB demonstrated significantly lower SNQ values in the ALSA group than in the ACLR group (FTG, 7.04 ± 3.65 vs 9.44 ± 4.51 [P = .006]; IAG, 6.62 ± 4.19 vs 8.77 ± 5.92 [P = .046]; TTG, 6.93 ± 3.82 vs 8.75 ± 4.55 [P = .040]). The SNQ values were significantly lower in the ALSA group for 2 of the 3 sections of the PLB (IAG, 7.73 ± 4.61 vs 9.88 ± 5.61 [P = .047]; TTG, 5.88 ± 3.10 vs 8.57 ± 4.32 [P = .001]). Partial lateral meniscectomy was correlated with higher SNQ values of the TTG in the AMB (β = 0.27; P = .009) and the PLB (β = 0.25; P = .008), with both groups pooled. Higher body mass index, smaller ACL graft-Blumensaat line angles, larger AMB graft diameters, and lower postoperative Tegner scores were also associated with inferior maturity in specific regions of the ACL graft.

CONCLUSION

A combination of ACLR and ALSA is a desirable option to improve the maturity of ACL grafts for patients who are young or expected to return to pivoting sports. Meanwhile, further investigations with higher levels of evidence and longer periods of follow-up are warranted.

A Modified Anatomic Transtibial Double-Bundle Anterior Cruciate Ligament Reconstruction Provides Reliable Bone Tunnel Positioning

Purpose

To evaluate the femoral and tibial tunnel positions via a modified anatomic transtibial double-bundle anterior cruciate ligament (ACL) reconstruction.

Methods

Patients who underwent double-bundle ACL reconstruction using the transtibial tunnel creation technique were identified. Double-bundle ACL reconstruction was performed for 94 knees using the transtibial tunnel creation technique. Tunnel aperture configurations and center positions of the anteromedial (AM) and posterolateral (PL) tunnels via postoperative 3-dimensional computed tomography were evaluated.

Results

There were 94 knees included. Regarding the intra-articular tunnel aperture configurations, the AM and PL tunnels overlapped at the femoral and tibial aperture in 66.0% and 94.7% cases, respectively. The mean femoral bone tunnel center was located at 23.0 ± 3.9% in the posterior-to-anterior ratio and 28.7 ± 6.0% in the proximal-to-distal ratio for the AM tunnels and at 32.8 ± 4.7% and 51.2 ± 5.2% for the PL tunnels, respectively. In the tibial tunnels, the mean AM tunnel center was located at 31.4 ± 3.6% in the anterior-to-posterior ratio and 44.3 ± 1.8% in the medial-to-lateral ratio and at 47.5 ± 3.8% and 44.3 ± 1.9% in the PL tunnel center, respectively. The femoral tunnels of outliers, both those created in nonanatomic positions as well as the posterior wall blowouts, were revealed in 7.4% cases. The nonanatomical bone tunnel group had significant heavier weight patients, lower tibial posterior slope, and were anterior in the AM and PL tunnel position. Posterior wall blowouts were related to posterior and proximal PL bone tunnel positions.

Conclusions

Modified transtibial double-bundle ACL reconstruction is a reliable tunnel creation technique with anatomic placement in 92.6% of the cases. The modification required that partially superimposing configuration of the 2 tibial tunnel apertures. The nonanatomic tunnels were related to patients of heavier weight and lower tibial posterior sloped knees, whereas the posterior wall blowouts were related to the posterior and proximal PL bone tunnel positions.

Level of Evidence

Level IV, therapeutic case series.

Remnant preservation with tensioning can improve the clinical outcome after anterior cruciate ligament reconstruction

BACKGROUND

Many studies exist about remnant preservation in anterior cruciate ligament (ACL) reconstruction. However, concern remains for development of a cyclops lesion during remnant preservation. To prevent this, a tensioning method has been suggested. Current study evaluated the clinical and radiologic results of remnant preservation in ACL reconstruction with tensioning compared to classical ACL reconstruction.

METHODS

From January 2016 to June 2017, ACL reconstruction patients who underwent magnetic resonance imaging (MRI) 2 years postoperatively were enrolled. For comparison, all participants were divided in two groups: remnant preservation with tensioning (group R) and controls (group C). Clinically, Hospital for Special Surgery (HSS), International Knee Documentation Committee (IKDC), Lysholm scores, and incidence of symptomatic cyclops lesions were evaluated. Radiologically, signal-to-noise quotient (SNQ) and size of the synovium on MRI as well as anterior instability in Telos stress radiographs were evaluated.

RESULTS

A total of 64 patients were enrolled (42 in group R and 22 in group C). The IKDC score in group R (70) was better than that in group C (62; p < 0.05). One patient in group R had a cyclops lesion with clinical symptoms and arthroscopic excision was recommended. Radiologically, the SNQ, synovium area, and anterior instability on Telos radiography showed no difference between the two groups.

CONCLUSION

Remnant preservation with tensioning is a good option for ACL reconstruction without the development of a cyclops lesion.

ACL Size, but Not Signal Intensity, Is Influenced by Sex, Body Size, and Knee Anatomy

Background:

Little is known about sex-based differences in anterior cruciate ligament (ACL) tissue quality in vivo or the association of ACL size (ie, volume) and tissue quality (ie, normalized signal intensity on magnetic resonance imaging [MRI]) with knee anatomy.

Hypothesis:

We hypothesized that (1) women have smaller ACLs and greater ACL normalized signal intensity compared with men, and (2) ACL size and normalized signal intensity are associated with age, activity levels, body mass index (BMI), bicondylar width, intercondylar notch width, and posterior slope of the lateral tibial plateau.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Knee MRI scans of 108 unique ACL-intact knees (19.7 ± 5.5 years, 62 women) were used to quantify the ACL signal intensity (normalized to cortical bone), ligament volume, mean cross-sectional area, and length. Independent t tests were used to compare the MRI-based ACL parameters between sexes. Univariate and multivariate linear regression analyses were used to investigate the associations between normalized signal intensity and size with age, activity levels, BMI, bicondylar width, notch width, and posterior slope of the lateral tibial plateau.

Results:

Compared with men, women had significantly smaller mean ACL volume (men vs women: 2028 ± 472 vs 1591 ± 405 mm³), cross-sectional area (49.4 ± 9.6 vs 41.5 ± 8.6 mm²), and length (40.8 ± 2.8 vs 38.1 ± 3.1 mm) (P < .001 for all), even after adjusting for BMI and bicondylar width. There was no difference in MRI signal intensity between men and women (1.15 ± 0.24 vs 1.12 ± 0.24, respectively; P = .555). BMI, bicondylar width, and intercondylar notch width were independently associated with a larger ACL (R² > 0.16, P < .001). Younger age and steeper lateral tibial slope were independently associated with shorter ACL length (R² > 0.03, P < .04). The combination of BMI and bicondylar width was predictive of ACL volume and mean cross-sectional area (R² < 0.3). The combination of BMI, bicondylar width, and lateral tibial slope was predictive of ACL length (R² = 0.39). Neither quantified patient characteristics nor anatomic variables were associated with signal intensity.

Conclusion:

Men had larger ACLs compared with women even after adjusting for BMI and knee size (bicondylar width). No sex difference was observed in signal intensity, suggesting no difference in tissue quality. The association of the intercondylar notch width and lateral tibial slope with ACL size suggests that the influence of these anatomic features on ACL injury risk may be partially explained by their effect on ACL size.

Registration:

NCT02292004 and NCT02664545 (ClinicalTrials.gov identifier).

Influence of Age on Signal Intensity of Magnetic Resonance Imaging and Clinical Outcomes in Double-Bundle Anterior Cruciate Ligament Reconstruction: Comparisons Among Different Age Groups

BACKGROUND

Thus far, the clinical results of anterior cruciate ligament (ACL) reconstruction have been observed to be comparable between young and older patients. In contrast, age-related changes in the structural and mechanical properties of tendons used for autografts have been described. However, age-related changes associated with graft maturation remain poorly understood.

HYPOTHESES

The hypotheses of this study were that (1) clinical outcomes after ACL reconstruction would be comparable between younger and relatively older patients and (2) younger patients would show lower signal intensity changes on magnetic resonance imaging scans indicative of graft maturation that would be better than that in relatively older patients.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively evaluated 236 patients who underwent double-bundle ACL reconstruction via the outside-in technique using hamstring autograft between January 2012 and December 2015. The patients were categorized by age into 3 groups: <20 years old, 20 to 39 years old, and ≥40 years old. Clinical outcomes were evaluated using the subjective International Knee Documentation Committee (IKDC) score, Tegner activity scale, Lysholm score, and objective assessment of joint laxity 24 months after surgery. In addition, graft maturation was evaluated using magnetic resonance imaging-derived measures of the signal intensity ratio (SIR) at 3, 6, 12, and 24 months postoperatively. Clinical outcomes and graft maturation were compared among the 3 groups.

RESULTS

The SIR of both bundles increased from 3 months to 12 months and decreased by 24 months, showing the same tendency in all groups. No significant difference was found in the SIR among the 3 groups at any time point (P > .05). The IKDC score was significantly lower in the ≥40-year group than in the <20-year group (P < .01). In contrast, no significant differences were noted in other clinical outcomes.

CONCLUSION

Patients aged ≥40 years exhibited lower IKDC scores compared with younger patients, although the results of graft maturation were comparable.

Radiographic alterations in clavicular bone tunnel width following anatomic coracoclavicular ligament reconstruction (ACCR) for chronic acromioclavicular joint injuries

PURPOSE

To evaluate tunnel widening and its relationship in loss of reduction and clinical outcomes in patients undergoing anatomic coracoclavicular ligament reconstruction (ACCR) using free tendon grafts for chronic acromioclavicular (AC) joint injuries.

METHODS

A retrospective chart review was performed on patients undergoing ACCR for type III-VI AC joint injuries between January 2003 and December 2017. For radiographic analysis, pre- and post-operative coracoclavicular distance (CCD) and tunnel width of the medial and lateral clavicular bone tunnel were measured at the earliest (EPO) and latest postoperative follow-up (LPO). To determine the clinical relevance of improvement in clinical outcome score (American Shoulder and Elbow Surgeons score) substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) thresholds were used.

RESULTS

Twenty-four patients with a mean clinical follow-up of 37 ± 35 months (mean age 44.7 ± 13.4) were included in the study. Both the medial (5.6 ± 0.2 mm_EPO-6.6 ± 0.7 mm_LPO; p < 0.001) and lateral (5.6 ± 0.5 mm_EPO-6.8 ± 1 mm_LPO; p < 0.001) clavicular bone tunnel showed significant widening from EPO to LPO. There was a significant loss of reduction at LPO (CCD_LPO 10.1 ± 4 mm) compared to EPO (CCD_EPO: 6.2 ± 3.8 mm) (p < 0.001). No significant correlation between loss of reduction and medial (p = 0.45; r = - 0.06) or lateral (p = 0.69; r = - 0.06) tunnel widening was found. Alterations in tunnel width were shown having no influence on clinical outcomes.

CONCLUSION

Patients who underwent ACCR using a free tendon graft for the treatment of chronic type III-VI ACJ injuries showed significant clavicular bone tunnel widening during the postoperative course. No correlation between tunnel widening and loss of reduction was shown with radiographic findings having no influence on clinical benefit and satisfaction.

STUDY DESIGN

Case Series; Level of evidence, IV.

Influence of femoral tunnel exit on the 3D graft bending angle in anterior cruciate ligament reconstruction

Purpose

To quantify the influence of the femoral tunnel exit (FTE) on the graft bending angle (GBA) and GBA-excursion throughout a full range of motion (ROM) in single-bundle anterior cruciate ligament (ACL) reconstruction.

Methods

Three-dimensional (3D) surface models of five healthy knees were generated from a weight-bearing CT obtained throughout a full ROM (0, 30, 60, 90, 120°) and femoral and tibial ACL insertions were computed. The FTE was simulated for 16 predefined positions, referenced to the Blumensaat's line, for each patient throughout a full ROM (0, 30, 60, 90, 120°) resulting in a total of 400 simulations. 3D GBA was calculated between the 3D directional vector of the ACL and the femoral tunnel, while the intra-articular ACL insertions remained unchanged. For each simulation the 3D GBA, GBA-excursion, tunnel length and posterior tunnel blow-out were analysed.

Results

Overall, mean GBA decreased with increasing knee flexion for each FTE (p < 0.001). A more distal location of the FTE along the Blumensaat's line resulted in an increase of GBA and GBA-excursion of 8.5 ± 0.6° and 17.6 ± 1.1° /cm respectively (p < 0.001), while a more anterior location resulted in a change of GBA and GBA-excursion of -2.3 ± 0.6° /cm (+ 0.6 ± 0.4°/ cm from 0–60° flexion) and 9.8 ± 1.1 /cm respectively (p < 0.001).

Mean tunnel length was 38.5 ± 5.2 mm (range 29.6–50.5). Posterior tunnel blow-out did not occur for any FTE.

Conclusion

Aiming for a more proximal and posterior FTE, with respect to Blumensaat’s line, reliably reduces GBA and GBA-excursion, while preserving adequate tunnel length. This might aid to reduce excessive graft stress at the femoral tunnel aperture, decrease femoral tunnel widening and promote graft-healing.

Level of Evidence

IV

Anatomic Double-Bundle Transtibial Anterior Cruciate Ligament Reconstruction

Double-bundle anterior cruciate ligament (ACL) reconstruction (DBACLR) is a reasonable transition from single-bundle ACL reconstruction to obtain better clinical outcomes, and most authors believe that it can only be performed through a medial portal. However, in our clinical practice, we have found that anatomic DBACLR can be performed easily and exactly through transtibial tunnels just by positioning the tibial tunnels appropriately. Thus, we would like to introduce this anatomic double-bundle transtibial ACL reconstruction technique, in which the most critical step is to create a shallow tibial tunnel for the anteromedial bundle with a proximal projection to the anatomic location of the corresponding femoral tunnel. We believe this Technical Note will give an interesting view of anatomic DBACLR.

A Hybrid Transtibial Technique Combines the Advantages of Anteromedial Portal and Transtibial Approaches: A Prospective Randomized Controlled Trial

BACKGROUND

The anteromedial (AM) portal and transtibial (TT) approaches are 2 common anterior cruciate ligament (ACL) femoral tunnel drilling techniques, each with unique benefits and disadvantages. A hybrid TT (HTT) technique using medial portal guidance of a flexible TT guide wire has recently been described that may combine the strengths of both the AM portal and the TT approaches.

HYPOTHESIS

The HTT technique will achieve anatomic femoral tunnel apertures similar to the AM portal technique, with improved femoral tunnel length and orientation.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 30 consecutive patients with primary ACL tears were randomized to undergo the TT, AM portal, or HTT technique for femoral tunnel positioning at the time of reconstruction. All patients underwent 3-dimensional computed tomography of the operative knee at 6 weeks postoperatively. Femoral and tibial tunnel aperture positions and tunnel lengths, as well as graft bending angles in the sagittal and coronal planes, were measured.

RESULTS

Tibial tunnel lengths and aperture positions were identical between the 3 groups. The AM portal and HTT techniques achieved identical femoral aperture positions in regard to both height (P = .629) and depth (P = .582). By contrast, compared with the AM portal and HTT techniques, femoral apertures created with the TT technique were significantly higher (P < .001 and P < .001, respectively) and shallower (P = .014 and P = .022, respectively) in the notch. The mean femoral tunnel length varied significantly between the groups, measuring 35.2, 41.6, and 54.1 mm for the AM portal, HTT, and TT groups, respectively (P < .001). Last, there was no difference between the mean coronal (P = .190) and sagittal (P = .358) graft bending angles between the TT and HTT groups. By contrast, compared with the TT and HTT techniques, femoral tunnels created with the AM portal technique were significantly more angulated in the coronal plane (17.7° [P < .001] and 12.5° [P = .006], respectively) and sagittal plane (13.5° [P < .001] and 10.5° [P = .013], respectively).

CONCLUSION

This prospective randomized controlled trial found that the HTT technique achieved femoral aperture positions equally as anatomic as the AM portal technique but produced longer, less angulated femoral tunnels, which may help reduce graft strain and mismatch. As such, this hybrid approach may represent a beneficial combination of both the TT and the AM portal techniques.

REGISTRATION

NCT02795247 (ClinicalTrials.gov identifier).

Changes in Cross-sectional Area and Signal Intensity of Healing Anterior Cruciate Ligaments and Grafts in the First 2 Years After Surgery

BACKGROUND

The quality of a repaired anterior cruciate ligament (ACL) or reconstructed graft is typically quantified in clinical studies by evaluating knee, lower extremity, or patient performance. However, magnetic resonance imaging of the healing ACL or graft may provide a more direct measure of tissue quality (ie, signal intensity) and quantity (ie, cross-sectional area).

HYPOTHESES

(1) Average cross-sectional area or signal intensity of a healing ACL after bridge-enhanced ACL repair (BEAR) or a hamstring autograft (ACL reconstruction) will change postoperatively from 3 to 24 months. (2) The average cross-sectional area and signal intensity of the healing ligament or graft will correlate with anatomic features of the knee associated with ACL injury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Patients with a complete midsubstance ACL tear who were treated with either BEAR (n = 10) or ACL reconstruction (n = 10) underwent magnetic resonance imaging at 3, 6, 12, and 24 months after surgery. Images were analyzed to determine the average cross-sectional area and signal intensity of the ACL or graft at each time point. ACL orientation, stump length, and bony anatomy were also assessed.

RESULTS

Mean cross-sectional area of the grafts was 48% to 98% larger than the contralateral intact ACLs at all time points (P < .01). The BEAR ACLs were 23% to 28% greater in cross-sectional area than the contralateral intact ACLs at 3 and 6 months (P < .02) but similar at 12 and 24 months. The BEAR ACLs were similar in sagittal orientation to the contralateral ACLs, while the grafts were 6.5° more vertical (P = .005). For the BEAR ACLs, a bigger notch correlated with a bigger cross-sectional area, while a shorter ACL femoral stump, steeper lateral tibial slope, and shallower medial tibial depth were associated with higher signal intensity (R² > .40, P < .05). Performance of notchplasty resulted in an increased ACL cross-sectional area after the BEAR procedure (P = .007). No anatomic features were correlated with ACL graft size or signal intensity.

CONCLUSION

Hamstring autografts were larger in cross-sectional area and more vertically oriented than the native ACLs at 24 months after surgery. BEAR ACLs had a cross-sectional area, signal intensity, and sagittal orientation similar to the contralateral ACLs at 24 months. The early signal intensity and cross-sectional area of the repaired ACL may be affected by specific anatomic features, including lateral tibial slope and notch width-observations that deserve further study in a larger cohort of patients.

REGISTRATION

NCT02292004 (ClinicalTrials.gov identifier).

Predictors of Healing Ligament Size and Magnetic Resonance Signal Intensity at 6 Months After Bridge-Enhanced Anterior Cruciate Ligament Repair

BACKGROUND

Primary repair of the anterior cruciate ligament (ACL) augmented with a tissue engineered scaffold to facilitate ligament healing is a technique under development for patients with ACL injuries. The size (the amount of tissue) and signal intensity (the quality of tissue) of the healing ligament as visualized on magnetic resonance imaging (MRI) have been shown to be related to its strength in large animal models.

HYPOTHESIS

Both modifiable and nonmodifiable risk factors could influence the size and signal intensity of the repaired ligament in patients at 6 months after surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

62 patients (mean age, 19.4 years; range, 14-35 years) underwent MRI of the knee 6 months after ACL repair augmented with an extracellular matrix scaffold. The signal intensity (normalized to cortical bone) and average cross-sectional area of the healing ligament were measured from the MRI stack obtained by use of a gradient echo sequence. Associations between these 2 measures and patient characteristics, which included demographic, clinical, and anatomic features, were determined by use of multivariable regression analysis.

RESULTS

A larger cross-sectional area of the repaired ligament at 6 months was associated with male sex, older age, and the performance of a larger notchplasty ( P < .05 for all associations). A lower signal intensity at 6 months, indicating greater similarity to normal ligament, was associated with a smaller tibial slope and greater side-to-side difference in quadriceps strength 3 months after surgery. Other factors, including preoperative body mass index, mechanism of injury, tibial stump length, and Marx activity score, were not significantly associated with either MRI parameter at 6 months.

CONCLUSION

Modifiable factors, including surgical notchplasty and slower recovery of quadriceps strength at 3 months, were associated with a larger cross-sectional area and improved signal intensity of the healing ACL after bridge-enhanced ACL repair in this preliminary study. Further studies to determine the optimal size of the notchplasty and the most effective postoperative rehabilitation strategy after ACL repair augmented by a scaffold are justified.

REGISTRATION

NCT02664545 (ClinicalTrials.gov identifier).