Signal intensity on magnetic resonance imaging after allograft double-bundle anterior cruciate ligament reconstruction

Predicting anterior cruciate ligament degeneration using magnetic resonance imaging: Insights from histological evaluation

BACKGROUND

Mucoid degeneration of the anterior cruciate ligament is a pathological condition that may impair knee mechanics and contribute to the symptomatology of osteoarthritis. This study aimed to evaluate whether preoperative magnetic resonance imaging can predict anterior cruciate ligament degeneration, specifically mucoid degeneration, and to elucidate the histopathological characteristics of mucoid degeneration in knee osteoarthritis patients.

METHODS

We evaluated a total of 95 knees of osteoarthritis patients (23 males, 72 females; mean age: 72.7 ± 7.5) scheduled for total knee arthroplasty. The relationship between preoperative magnetic resonance imaging findings and the histopathological evidence of anterior cruciate ligament mucoid degeneration was examined. Immunohistochemical analysis was employed for collagen types (COL-I, COL-II), chondrogenesis (SOX9), and vascularity (CD31).

RESULTS

High signal intensity on magnetic resonance imaging showed a positive correlation with Alcian Blue staining areas (rs = 0.59, p < 0.01) and the swelling index (rs = 0.62, p < 0.01), indicating advanced mucoid degeneration. The absence of synovial lining around the anterior cruciate ligament was associated with more severe degeneration. In the histological evaluations, advanced degeneration was characterized by an increase in chondroid metaplasia and collagen disorientation. The Alcian Blue and SOX9 correlation was positive (rs = 0.69, p < 0.01), but negative with COL-I (rs = -0.38, p = 0.03) and vascularity (CD31) (rs = -0.60, p < 0.01).

CONCLUSIONS

Preoperative magnetic resonance imaging is an effective tool in assessing the severity of anterior cruciate ligament degeneration; it influences surgical decisions. High signal intensity on magnetic resonance images denotes advanced mucoid degeneration. The absence of synovial lining around the anterior cruciate ligament is associated with more severe degeneration and may accelerate degenerative changes. Chondroid metaplasia and collagen disorientation mark advanced degeneration. Magnetic resonance imaging can be used to gauge the degree of anterior cruciate ligament degeneration in osteoarthritis.

Association Between Tunnel Position, Tunnel Angle, Graft Signal Intensity, and Graft Thickness in the Reconstructed Posterior Cruciate Ligament

Background

An appropriate tunnel position, tunnel angle, and tunnel-graft angle are important factors for maintaining the stability and mechanical properties of a posterior cruciate ligament (PCL) graft.

Purpose

To evaluate the association between tunnel position, tunnel angle, graft signal intensity ratio (SIR), and graft thickness after remnant-preserving PCL reconstruction.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were patients who had undergone remnant-preserving single-bundle PCL reconstruction using a tibialis anterior allograft between March 2014 and September 2020 and who had minimum 12-month postoperative magnetic resonance imaging scans. Tunnel position and angle were evaluated via 3-dimensional computed tomography, and their association with graft SIR on both the femoral and the tibial sides was determined. Graft thickness and SIR at 3 areas of the graft were evaluated and compared, and their association with tunnel-graft angle was also determined.

Results

Overall, 50 knees (50 patients; 43 male, 7 female) were included. The mean time to postoperative magnetic resonance imaging was 25.8 ± 15.8 months. The mean SIR of the graft's midportion was higher compared with that of the proximal and distal portions (P = .028 and P < .001, respectively), and the SIR of the proximal portion was higher compared with that of the distal portion (P = .002). The femoral tunnel-graft angle was more acute than the tibial tunnel-graft angle (P = .004). A more anteriorly and distally located femoral tunnel led to a less acute femoral tunnel-graft angle (P = .005) and a decreased SIR of the proximal portion (P = .040), and a more laterally located tibial tunnel was associated with a less acute tibial tunnel-graft angle (P = .024) and a reduced SIR of the distal portion (P = .044). The mean thicknesses of the graft's midportion and distal portion were larger than that of the proximal portion (P < .001). The SIR of the graft's midportion was positively correlated with its thickness (r = 0.321; P = .023).

Conclusion

The SIR of the proximal portion of the graft around the femoral tunnel was higher than that of the distal portion around the tibial tunnel. An anteriorly and distally positioned femoral tunnel and a laterally positioned tibial tunnel resulted in less acute tunnel-graft angles that were associated with decreased signal intensity.

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.

In situ cross-sectional area of the quadriceps tendon using preoperative magnetic resonance imaging significantly correlates with the intraoperative diameter of the quadriceps tendon autograft

PURPOSE

Preoperative assessment to determine the sizes of potential autografts is necessary for individualized anterior cruciate ligament reconstruction (ACLR). However, no study has investigated the prediction of the intraoperative diameter of the quadriceps tendon (QT) autograft based upon preoperative imaging. This study investigated the correlation between the intraoperative diameter of a QT autograft and in situ thickness or cross-sectional area (CSA) measured using preoperative MRI.

METHODS

Thirty-one knees of 31 patients (mean age 20.9 ± 5.0 years) who underwent individualized anatomic ACLR using all soft tissue QT autograft were included retrospectively. At 15 mm proximal to the superior pole of the patella, the maximum QT thickness was assessed in the sagittal plane and the CSA was assessed at the central 10 mm of the QT in the axial plane. The angle between the axial plane and a line perpendicular to the QT longitudinal axis was used to calculate an adjusted CSA using a cosine function. Intraoperatively, each QT autograft was harvested with 10 mm width and the diameter was measured using a graft sizing device.

RESULTS

Intra- and inter-observer reliabilities of all measurements using preoperative MRI were excellent (intra-class correlation coefficient, 0.833-0.970). Significant correlations were observed between the thickness, CSA, or adjusted CSA, and the intraoperative diameter (R = 0.434, 0.607, and 0.540, respectively; P < 0.05).

CONCLUSIONS

The CSA correlated most strongly with the QT autograft diameter. For individualized anatomic ACLR, measuring in situ CSA can be useful for preoperative planning of appropriate graft choices prior to surgery.

LEVEL OF EVIDENCE

III.

The relationship between graft synovialization and graft revascularization after ACL reconstruction: Assessment using dynamic contrast enhanced-MRI and second-look arthroscopy

PURPOSE

To assess graft vascularity via dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) at 1-year and 2-year postoperatively and to evaluate the relationship between the vascularity using DCE-MRI and the synovialization using second-look arthroscopy.

MATERIALS AND METHODS

Fifty-four patients from prospective data included who underwent anterior cruciate ligament reconstruction (ACLR) and DCE-MRI. The graft was divided into proximal, middle, and distal zones; average of three zones was calculated. Signal/noise quotient (SNQ) was measured on proton-density image and normalized area under the curve (nAUC) was calculated from DCE-MRI. The results at 1-year (SNQ-1 and nAUC-1) and 2-year (SNQ-2 and nAUC-2) postoperatively were compared between two time points. Forty-one patients underwent second-look arthroscopy were classified into three groups according to the synovialization: Excellent (n = 17), Fair (n = 16), and Poor (n = 8). The SNQs and nAUCs were compared between three groups.

RESULTS

Fifty-four and 23 patients underwent DCE-MRI at 1-year and 2-year, respectively. A significant decrease was observed from nAUC_average-1 to nAUC_average-2 (95 % confidential interval, 0.4-2.3; P = .007). Both SNQ_average-1 and SNQ_average-2 were significantly lower in the excellent than in the poor (SNQ_average-1, P < .001; SNQ_average-2, P = .003). Both SNQ_average-1 and SNQ_average-2 were significantly lower in the fair than in the poor (SNQ_average-1, P=.032; SNQ_average-2, P = .012). Both nAUC_average-1 and nAUC_average-2 were significantly higher in the excellent than in the poor (nAUC_average-1, P < .001; nAUC_average-2, P = .010). The nAUC_average-1 was significantly higher in the excellent than the fair (nAUC_average-1, P < .001).

CONCLUSION

Well-synovialized grafts showed significantly lower SNQs and significantly higher nAUCs than did poor-synovialized grafts based on the second-look arthroscopic findings. We can indirectly infer from this result that well-synovialized grafts may have better biomechanical properties.

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

PURPOSE

To evaluate and compare the femoral tunnel aperture position, graft bending angle and the magnetic resonance imaging (MRI) graft signal intensity after anatomical double-bundle anterior cruciate ligament (ACL) reconstruction between transtibial and transportal drilling techniques of the femoral tunnel.

METHODS

Eighty-seven patients who underwent anatomic double-bundle ACL reconstruction with hamstring tendon autograft between January 2012 and December 2014 were included in this retrospective study. Forty-one patients underwent reconstruction using a transportal technique (TP group) and 46 patients underwent reconstruction using a transtibial technique (TT group). The anteromedial (AM) femoral aperture position and the graft bending angle were assessed using transparent three-dimensional CT 2 weeks postoperatively. MRI assessment was performed with proton density-weighted images in an oblique coronal plane 6 and 12 months postoperatively. Signal/noise quotient was calculated for two specific graft sites (femoral tunnel site and mid-substance site). Femoral aperture position, the graft bending angle and signal/noise quotient were compared between the TP and TT groups.

RESULTS

There was no significant difference in the aperture position between the two groups. The graft bending angle of the AM tunnel in the axial plane was significantly greater in the TP group (p < 0.001). On the other hand, the TP group had a significantly more acute angle in the coronal plane (p < 0.001). There was no significant difference at either site in the signal/noise quotient of the graft between the two groups at 6 months. However, the TT group had a lower signal/noise quotient at 12 months at both sites (femoral aperture: p = 0.04, mid-substance: p = 0.004).

CONCLUSION

There was a significant difference in signal/noise quotient between the two drilling techniques 12 months postoperatively. There was no significant difference in femoral tunnel aperture position between the two groups. However, graft bending angle at the femoral tunnel aperture was significantly different between the two groups, indicating the possibility that graft bending angle is a factor that influences graft maturation. This indicates that the TT technique has an advantage over the TP technique in terms of graft maturation.

Inferior graft maturity in the PL bundle after autograft hamstring double-bundle ACL reconstruction

PURPOSE

The purpose of this study was to evaluate the signal/noise quotient (SNQ) for graft maturation and the serial changes observed in the magnetic resonance imaging (MRI) findings after double-bundle (DB) anterior cruciate ligament (ACL) reconstruction using a hamstring tendon autograft at a minimum of 5 years after surgery.

METHODS

Forty-five patients who underwent DB ACL reconstruction between 2007 and 2010 were included in this prospective study. All participants underwent postoperative MRI at 3 weeks and 3, 6, 9 and 12, 18, 24, 36, 48 and 50 months. The signal intensity (SI) characteristics of the reconstructed graft were evaluated on oblique axial proton density-weighted MR imaging (PDWI) perpendicular to the grafts. The signal/noise quotient (SNQ) was calculated to quantitatively determine the normalized SI. The SNQ of the AMB and PLB was evaluated separately.

RESULTS

The mean SNQ of the AM bundle (AMB) continued to increase until 6 months after surgery (5.2 ± 1.2), and then gradually decreased and became well stabilized by 18 months (3.3 ± 0.5), after which it remained unchanged. On the other hand, the mean SNQ of the PL bundle (PLB) continued to increase until 9 months after surgery (6.2 ± 1.1), and then decreased incrementally and became well stabilized by 24 months (4.1 ± 0.5). The SI of PLB was significantly higher than that of AMB between 3 and 24 months (p = 0.04, 0.03, 0.01, 0.04, 0.02 and 0.03, respectively).

CONCLUSIONS

These results indicate that at least 18 months is needed after ACL reconstruction to sufficiently restore the SI of the AMB, while at least 24 months are needed to for the PLB. The SI of the PLB was significantly higher than that of the AMB at 3-24 months after surgery, indicating that the PLB showed inferior graft maturity to the AMB until 24 months after surgery. For clinical relevance, the correct understanding of serial changes in graft maturation may potentially be used in decision-making regarding a return to sports.

LEVEL OF EVIDENCE

Prospective case series, Level IV.

Hamstring tendon autografts do not show complete graft maturity 6 months postoperatively after anterior cruciate ligament reconstruction

PURPOSE

In this prospective, double-center cohort study, we aim to assess how the anterior cruciate ligament (ACL) signal intensity on magnetic resonance imaging (MRI) potentially varies between a group of patients with anatomic ACL reconstruction using autogenous hamstring grafts 6 months postoperatively and a healthy ACL control group, and how MRI-based graft signal intensity is related to knee laxity.

METHODS

Sixty-two consecutive patients who underwent ACL reconstruction using quadrupled hamstring tendon autograft were prospectively invited to participate in this study, and they were evaluated with MRI after 6 months of follow-up. 50 patients with an MRI of their healthy ACL (Clinica Luganese, Lugano, Switzerland) and 12 patients of their contralateral healthy knee (Department of Orthopaedic and Trauma Surgery, Medical University of Vienna, Austria) served as the control group. To evaluate graft maturity, the signal-to-noise quotient (SNQ) was measured in three regions of interest (ROIs) of the proximal, mid-substance and distal ACL graft and the healthy ACL. KT-1000 findings were obtained 6 months postoperatively in the ACL reconstruction group. Statistical analysis was independently performed to outline the differences in the two groups regarding ACL intensity and the correlation between SNQ and KT-1000 values.

RESULTS

There was a significant difference in the mean SNQ between the reconstructed ACL grafts and the healthy ACLs in the proximal and mid-substance regions (p = 0.001 and p = 0.004). The distal region of the reconstructed ACL showed a mean SNQ similar to the native ACL (n.s). Patients with a KT-1000 between 0 and 1 mm showed a mean SNQ of 0.1; however, a poor correlation was found between the mean SNQ and KT-1000 findings, probably due to the small sample size of patients with higher laxity.

CONCLUSION

After 6 months of follow-up, hamstring tendon autografts for anatomic ACL reconstruction do not show equal MRI signal intensity compared to a healthy ACL and should therefore be considered immature or at least not completely healed even if clinical laxity measurement provides good results. However, in the case of a competitive athlete, who is clinically stable and wants to return to sports at 6 months, performing an MRI to confirm the stage of graft healing might be an option.

LEVEL OF EVIDENCE

Prospective, comparative study II.

Time From Injury to Surgery Affects Graft Maturation Following Posterior Cruciate Ligament Reconstruction With Remnant Preservation: A Magnetic Resonance Imaging-Based Study

PURPOSE

To evaluate the clinical outcomes and graft maturation following posterior cruciate ligament reconstruction (PCLR) with preserved remnant and further analyze the correlated factors affecting graft maturation.

METHODS

Consecutive patients who underwent unilateral single-bundle PCLR with remnant preservation from January 2011 to October 2014 by the same senior doctor using tibialis anterior allografts and same surgical technique were included. At a follow-up of more than 2 years, range of motion (ROM) and posterior laxity assessed by posterior drawer test and the KT-1000 arthrometer were examined. Tegner, Lysholm, and International Knee Documentation Committee scores were evaluated. The graft maturation was assessed by a 3.0-T magnetic resonance imaging. Overall correlation analyses and multivariate regression analysis were performed to identify correlated factors of graft maturation, and then subgroups were divided and analyzed according to significant risk factor.

RESULTS

Forty-three (84.3%) of 51 enrolled patients were successfully followed up (38.4 months, 24-54 months). All clinical scores improved significantly, and there were no complications. The results of KT-1000 difference revealed significant decline of posterior laxity (9.4 ± 1.5 vs 2.2 ± 1.5 mm; P < .001). The MRI evaluation confirmed no ligament retears. Both correlation and regression analyses showed time from injury to surgery had a positive, statistically significant weak correlation with the signal intensity score (R = 0.38, P = .012; coefficient = 0.10; P = .036). Subgroup (group 1: time from injury to surgery <3 months; group 2: 3-6 months; group 3: 6-12 months; group 4: ≥12 months) analysis showed there were no significant differences of clinical outcomes between subgroups, while MRI signal intensity was significantly lower in the group with shorter time from injury to surgery (P = .02).

CONCLUSIONS

The remnant-preserved PCLR resulted in satisfactory clinical outcomes and graft maturation at a mean follow-up of 38.4 months. The time from injury to surgery showed a weak positive correlation with postoperative graft signal intensity on MRI.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Can we predict the size of frequently used autografts in ACL reconstruction?

PURPOSE

This study presents a method to measure the size of quadriceps, patellar tendon and hamstring autografts using preoperative magnetic resonance imaging (MRI).

METHODS

Sixty-two subjects with a mean age of 25 ± 10 years who underwent ACL surgery between 2011 and 2014 were included. Patient anthropometric data were recorded for all subjects. During surgery, the respective autograft was harvested and measured using commercially available graft sizers. MRI measurements were performed by two raters, who were blinded to the intra-operative measurements.

RESULTS

The inter- and intra-rater reliability was ≥0.8 for all MRI measurements. The intra-class correlation coefficient between the MRI measurement of the graft and the actual size of the harvested graft was 0.639. There were significant correlations between quadriceps tendon thickness and height (r = 0.3, p < 0.03), weight (r = 0.3, p < 0.01), BMI (r = 0.3, p < 0.04) and gender (r = -0.4, p < 0.002) and patellar tendon thickness and height (r = 0.4, p < 0.01), weight (r = 0.3, p < 0.01) and gender (r = -0.4, p < 0.012).

CONCLUSION

Preoperative MRI measurements of quadriceps, patellar tendon and hamstring graft size are highly reliable with moderate-to-good accuracy. Significant correlations between patient anthropometric data and the thicknesses of the quadriceps and patellar tendons were observed. Obtaining this information can be useful for preoperative planning and to help counsel patients on appropriate graft choices prior to surgery.

LEVEL OF EVIDENCE

III.

Tunnel positioning assessment after anterior cruciate ligament reconstruction at 12months: Comparison between 3D CT and 3D MRI. A pilot study

BACKGROUND

Tunnel positioning assessment is a major issue after anterior cruciate ligament (ACL) reconstruction surgery. Historically, it used plain X-ray and, more recently, CT with 3D reconstruction. MRI is a reliable method of assessing ACL graft integrity and postoperative complications. To our knowledge, there have been no studies of efficacy in tunnel positioning assessment. The aim of this study was to assess the efficacy of 3D MRI in assessing femoral and tibial tunnel positioning after ACL reconstruction. The hypothesis was that 3D MRI sequences with reconstruction are as accurate as 3D CT for tunnel positioning assessment in ACL reconstruction.

METHODS

Twenty-two patients who underwent an arthroscopic ACL reconstruction using hamstring graft were included in a prospective study. All patients were examined on 3D CT and 3D MRI at 12months post-surgery. Tunnel positioning was assessed on both imaging systems by a musculoskeletal radiologist and an orthopedic surgeon specialized in knee arthroscopy, both blind to all clinical data.

RESULTS

No statistically significant difference was found between 3D CT and 3D MRI on coronal and sagittal reconstructions. For coronal assessment of tibial tunnel orifice, sagittal assessment of tibial tunnel orifice and sagittal assessment of femoral tunnel orifice, P-values ranged from 0.37 to 0.99, 0.051 to 0.64 and 0.19 to 0.59, respectively. For tibial and femoral tunnel angulation, P-values were respectively 0.52 and 0.29.

CONCLUSION

3D MRI is a reliable method to assess femoral and tibia tunnel positioning in ACL reconstruction, compared to 3D CT as gold standard. Indeed, in our opinion 3D MRI could in the future replace CT for ACL reconstruction assessment, concerning not only the meniscus and ligaments but also tunnel position.

LEVEL OF EVIDENCE

Level 3; comparative prospective study.

Tibial ACL insertion site length: correlation between preoperative MRI and intra-operative measurements

PURPOSE

This study was undertaken primarily to identify the tibial insertion site length of ruptured ACL fibres in patients undergoing primary ACL reconstruction. A secondary aim was to evaluate the correlation of pre- and intra-operative measurements.

METHODS

In 146 patients undergoing primary ACL reconstruction, a preoperative measurement on MRI of the tibial ACL insertion site length was taken by two raters and then compared with single surgeon's intra-operative measurements using a specialized ruler. Inclusion criteria were primary ACL reconstruction and MRI performed within 3 months prior to surgery on one specific MRI machine at the study centre. Inter-rater and intra-rater reliability based on intra class correlation (ICC) was calculated. Additionally, correlation between preoperative and postoperative measurements and the anthropometric data was assessed using Pearson correlation.

RESULTS

The tibial ACL insertion site had a mean length of 16.6 ± 1.6 mm (11.9-21.0) as measured by MRI, and 16.4 ± 1.6 mm (11.0-20.0) as measured intra-operatively. The ICCs for intra- and inter-rater reliability of the MRI measurements were 0.99 (95 % CI 0.97; 0.99; p < 0.001) and 0.81 (95 % CI 0.75; 0.86; p < 0.001), respectively. Regression analysis demonstrated, after controlling for subject height and weight, that the MRI measurements significantly predicted intra-operative measurement of tibial insertion site length (β = 0.796; R (2)-change 0.77; p < 0.001).

CONCLUSION

Preoperative measurement of the tibial ACL length is possible using MRI and can be a valuable aid in more efficient preoperative planning given the knowledge of expected dimensions of special knee structures.

LEVEL OF EVIDENCE

III.

Individualized anatomic anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) injuries are often seen in young participants in sports such as soccer, football, and basketball. Treatment options include conservative management as well as surgical intervention, with the goal of enabling the patient to return to cutting and pivoting sports and activities. Individualized anatomic ACL reconstruction is a surgical technique that tailors the procedure to the individual patient using preoperative measurements on plain radiographs and magnetic resonance imaging and intraoperative measurement to map the patients' native ACL anatomy in order to replicate it as closely as possible. Anatomic ACL reconstruction, therefore, is defined as reconstruction of the ACL to its native dimensions, collagen orientation, and insertion site. The surgical reconstruction is followed by a specific rehabilitation protocol that is designed to enable the patient to regain muscle strength and proprioception while facilitating healing of the reconstructed ACL prior to the patient's returning to sports activities.

Correlation Analysis of Potential Factors Influencing Graft Maturity After Anterior Cruciate Ligament Reconstruction

Background:

Postoperatively, signal changes of the reconstructed anterior cruciate ligament (ACL) graft on magnetic resonance imaging (MRI) images commonly occurs, which may be a cause for concern. The signal intensity changes are usually expressed by signal/noise quotient (SNQ) value, representing graft maturity. To date, little is known about the factors influencing the SNQ value of the reconstructed ACL graft.

Purpose:

To evaluate ACL graft SNQ value and associated factors after ACL reconstruction.

Study Design:

Case series; Level of evidence, 4.

Methods:

Male patients who underwent ACL reconstruction using autograft or allograft tendon from September 2004 to September 2011 were randomly invited to take part in this investigation, including functional scores, physical examination, and MRI scan. The femoral side graft was fixed with Endobutton CL or Rigidfix pins, and the tibial side graft was fixed with a bio-intrafix. SNQ values of each graft were measured on MRI to represent graft maturity. Sagittal ACL angle, ACL–Blumensaat line angle, and medial and lateral posterior tibial slope (PTS) were measured using MRI 3-dimensional dual-echo steady-state images. Potential risk factors, including age, body mass index, postoperative time, Tegner activity scale (TAS), sagittal ACL angle, ACL–Blumensaat line angle, medial PTS, lateral PTS, and primary graft diameter, were tested for their association with the graft SNQ value by multivariate stepwise regression analysis.

Results:

A total of 104 male subjects (mean follow-up, 30.7 months) were examined, including 62 allograft and 42 autograft reconstructions. There was a significant association between graft SNQ and postoperative time (r = −0.431, P < .001), TAS (r = 0.295, P = .002), and ACL–Blumensaat line angle (r = −0.304, P = .002). Univariate regression analysis showed that TAS (β = 6.15, P < .001) positively correlated, postoperative time (β = −0.26, P < .001) negatively correlated, and ACL–Blumensaat line angle (β = −0.40, P = .038) negatively correlated with graft SNQ. Multivariate stepwise regression analysis showed that TAS, postoperative time, ACL–Blumensaat line angle, and age were significant independent factors associated with graft SNQ.

Conclusion:

The graft SNQ value had a significant positive correlation with physical activity level and a significant negative correlation with postoperative time in this study. Males with a shorter postoperative time and a higher physical activity level had higher graft signal intensity postoperatively.