Tendon healing in a bone tunnel differs at the tunnel entrance versus the tunnel exit: an effect of graft-tunnel motion?

Gradual stabilization and narrowing of bone tunnels following primary anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study is to dynamically assess variations in tunnel diameters following anterior cruciate ligament reconstruction (ACLR) and investigate correlations with patient-reported outcomes (PROs) and graft maturity based on signal-to-noise quotient (SNQ).

METHODS

Tunnel diameter and tunnel position were measured using three-dimensional models derived from computed tomography (CT) data. Postoperative graft maturity and integration were evaluated using magnetic resonance imaging (MRI). Clinical outcomes were assessed through PROs, which included the International Knee Documentation Committee Subjective Knee Evaluation Form, Knee Injury and Osteoarthritis Outcome Scores and Lysholm scores. The correlation between tunnel enlargement extent, PROs and SNQ values, as well as correlations between confounding factors, tunnel diameter differences and SNQ were analyzed.

RESULTS

A total of 73 participants underwent primary ACLR and scheduled follow-ups. At the segment of the articular aperture, the femoral tunnel was enlarged by 32.3% to 10.4 ± 1.6 mm (p < 0.05), and the tibial tunnel was widened by 17.2% to 9.6 ± 1.2 mm (p < 0.05) at the 6-month follow-up. At 1 year postoperatively, diameters at the articular aperture were not further increased on the femoral (n.s.) and tibial (n.s.) sides. In early postoperative follow-up, the femoral tunnel was anteriorly and distally shifted, coupled with posterior and lateral deviation involving the tibial side, exhibiting minimal migration at 1-year follow-up. The degree of tunnel widening was not correlated with PROs and SNQ values. Age, gender, body mass index (BMI), time from surgery to follow-up, concomitant injuries and autograft type were not correlated with tunnel diameter differences and SNQ.

CONCLUSIONS

The femoral and tibial bone tunnels exhibited eccentrical widening and gradually stabilized at 1 year following ACLR. Furthermore, the enlarged bone tunnels were not correlated with unsatisfied PROs and inferior graft maturity.

LEVEL OF EVIDENCE

Level IV.

Repair potential of self-assembling peptide hydrogel in a mouse model of anterior cruciate ligament reconstruction

Purpose

Establishing zonal tendon-to-bone attachment could accelerate the anterior cruciate ligament reconstruction (ACLR) rehabilitation schedule and facilitate an earlier return to sports. KI24RGDS is a self-assembling peptide hydrogel scaffold (SAPS) with the RGDS amino acid sequence. This study aimed to elucidate the therapeutic potential of KI24RGDS in facilitating zonal tendon-to-bone attachment after ACLR.

Methods

Sixty-four C57BL/6 mice were divided into the ACLR + SAPS and ACLR groups. ACLR was performed using the tail tendon. To assess the maturation of tendon-to-bone attachment, we quantified the area of mineralized fibrocartilage (MFC) in the tendon graft with demeclocycline. Immunofluorescence staining of α-smooth muscle actin (α-SMA) was performed to evaluate progenitor cell proliferation. The strength of tendon-to-bone attachment was evaluated using a pull-out test.

Results

The MFC and maximum failure load in the ACLR + SAPS group were remarkably higher than in the ACLR group on Day 14. However, no significant difference was observed between the two groups on Day 28. The number of α-SMA-positive cells in the tendon graft was highest on Day 7 after ACLR in both the groups and was significantly higher in the ACLR + SAPS group than in the ACLR group.

Conclusion

This study highlighted the latent healing potential of KI24RGDS in facilitating early-stage zonal attachment of tendon grafts and bone tunnels post-ACLR. These findings may expedite rehabilitation protocols and shorten the timeline for returning to sports.

Level of Evidence

Not applicable.

Presoaking Grafts in Vancomycin Does Not Impair Graft-Bone Healing in a Rat Anterior Cruciate Ligament Reconstruction Model

BACKGROUND

The vancomycin presoaking technique (wherein grafts are treated with a vancomycin solution [VS] for anterior cruciate ligament reconstruction [ACLR]) reduces the infection rate after ACLR. However, the effects of this technique on graft-bone healing have not been fully elucidated.

PURPOSE

To investigate the effects of vancomycin presoaking on graft-bone healing in a rat ACLR model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Long flexor digitorum longus tendons were obtained from 9 Wistar rats, and each was randomly allocated to the normal saline (NS) or VS groups. The grafts were immersed in sterile saline for 30 minutes in the NS group and in a 5-mg/mL VS in the VS group. The presence of time-zero graft bacterial contamination was confirmed, and the grafts were incubated in Fluidised Thioglycollate Broth for 2 weeks. ACLR was performed on the right knees of 65 male Wistar rats using the flexor digitorum longus tendons. Each graft was similarly treated. Biomechanical testing, micro-computed tomography, and histological evaluations were performed 4 and 12 weeks postoperatively.

RESULTS

The VS group showed significantly reduced graft contamination at time zero (P = .02). The mean maximum loads to failure were 13.7 ± 8.2 N and 11.6 ± 4.8 N in the NS and VS groups, respectively, at 4 weeks (P = .95); and 23.2 ± 13.2 N and 30.4 ± 18.0 N in the NS and VS groups, respectively, at 12 weeks (P = .35). Regarding micro-computed tomography, the mean bone tunnel volumes were 3.76 ± 0.48 mm3 and 4.40 ± 0.58 mm3 in the NS and VS groups, respectively, at 4 weeks (P = .41); and 3.51 ± 0.38 mm3 and 3.67 ± 0.35 mm3 in the NS and VS groups, respectively, at 12 weeks (P = .54). Histological semiquantitative examination revealed no clear between-group differences at any time point.

CONCLUSION

Presoaking grafts in vancomycin in a rat ACLR model demonstrated no discernible adverse effects on short- and midterm biomechanical, radiological, and histological investigations.

CLINICAL RELEVANCE

The findings provide guidance for surgeons when considering this technique.

Hyperbaric oxygen therapy enhances graft healing and mechanical properties after anterior cruciate ligament reconstruction: An experimental study in rabbits

Hyperbaric oxygen therapy (HBOT) has proven successful in wound healing. However, its potential effects on anterior cruciate ligament (ACL) injuries remain uncertain. This study aimed to investigate the impact of HBOT on graft healing following ACL reconstruction in rabbits. Male New Zealand rabbits underwent ACL reconstruction and were randomly divided into two groups: the HBOT group and the ambient air group. The HBOT group received 100% oxygen at 2.5 atmospheres absolute for 2 h daily for 5 consecutive days, starting from the first day after surgery. The ambient air group was maintained in normal room air throughout the entire period. After 12 weeks following the surgery, animals were euthanized, and their knees were harvested for analysis. The HBOT group demonstrated superior graft maturation and integration in comparison to the ambient air group, as evidenced by lower graft signal intensity on magnetic resonance imaging, decreased femoral and tibial tunnel size, and higher bone mineral density values on high-resolution peripheral quantitative computed tomography scans. Additionally, biomechanical testing indicated that the HBOT group had greater load to failure and stiffness values than the ambient air group. In conclusion, the adjuvant use of HBOT improved ACL graft maturation and integration, reduced tunnel widening, and enhanced the biomechanical properties of the graft. These results may provide important insights into the potential clinical application of HBOT as a therapeutic intervention to enhance graft healing after ACL reconstruction, paving the way for further research in this area.

Comparison of the Clinical Outcomes between All-inside and Standard Technique in Anterior Cruciate Ligament Reconstruction with 6-strand Hamstring Tendon Autograft

OBJECTIVE

All-inside and standard techniques with 4-strand hamstrings graft have been widely used in anterior cruciate ligament (ACL) reconstruction. However, the graft diameter of less than 8 mm will significantly increase the rate of surgical failure, and the 6-strand graft can solve this problem. The purpose of this study is to compare all-inside ACL reconstruction using suspensory cortical button fixation on both tibia and femur with standard ACL reconstruction using suspensory femoral fixation and a bioabsorbable tibial interference screw with a 6-strand hamstring tendon autograft in postoperative clinical outcomes.

METHODS

From January 2020 to December 2020, 48 patients performed ACL reconstruction were divided into the all-side group and the standard group according to the different surgical techniques. Magnetic resonance imaging (MRI) and subjective function scores was used to assess clinical outcomes at least 24 months following ACL reconstruction. MRI was used to measure the value of bone tunnel widening in articular and middle portions. Subjective function scores included the Lysholm knee score, the International Knee Documentation Committee (IKDC) score, the Knee Society Score (KSS) for pain and function, and KT-1000. The t-test was used assuming the distribution of the patients which follows the normal distribution and we used non-parametric tests if these two conditions were not satisfied.

RESULTS

At the final follow-up, there were 22 patients in the all-inside group and 24 patients in the standard group. No significant differences were found with respect to femoral tunnel widening and subjective function scores. However, a significant increase in tibial tunnel widening was found in the middle portion of the standard group (2.25 ± 0.74) compared to the all-inside group (0.76 ± 0.24) (p < 0.01) and also in the articular portion of the standard group (2.07 ± 0.77) compared to the all-inside group (1.52 ± 0.54) (p = 0.02). In addition, the value of the KT-1000 was 1.81 ± 0.45 for the all-inside group and 2.12 ± 0.44 in the standard group (p = 0.016).

CONCLUSION

The objective stability of the knee was relatively better in the all-inside group than in the standard group. And tunnel widening after ACL reconstruction was significantly greater in the standard technique when compared to the all-inside technique on the tibia side.

Triple Hybrid Tibial Anterior Cruciate Ligament Graft Fixation

Optimal graft fixation in anterior cruciate ligament reconstruction is critical. Several direct and indirect methods of graft fixation exist, each with advantages and disadvantages. This Technical Note describes a tibial hybrid anterior cruciate ligament graft fixation technique combining direct and indirect fixation methods, including autologous bone augmentation of the drill tunnel using cancellous bone fragments.

Tunnel widening after ACL reconstruction with different fixation techniques: aperture fixation with biodegradable interference screws versus all-inside technique with suspensory cortical buttons. 5-year data from a prospective randomized trial

BACKGROUND

The aim of the present study was to examine tunnel widening and clinical outcomes after anterior cruciate ligament reconstruction (ACLR) using two different fixation methods: aperture fixation with biodegradable interference screws versus all-inside ACLR with suspensory cortical buttons.

METHODS

Tunnel widening was assessed using volumetric and diameter measurements on magnetic resonance imaging (MRI) scans directly after surgery, as well as 6 months and 2 and 5 years postoperatively. Clinical outcomes were assessed after 5 years with instrumented tibial anteroposterior translation measurement (KT-1000), single-leg hop testing, and the IKDC, Lysholm, and Tegner activity scores.

RESULTS

At the final follow-up, the study population consisted of 21 patients, 12 of whom underwent screw fixation and 9 of whom had button fixation. 3 patients with all-inside ACLR had sustained early repeat ruptures within 6 months after surgery and had to be excluded from the further analysis. With screw fixation, the tibial tunnel volume changed significantly more over time compared to all-inside button fixation, with a larger initial increase at 6 months (from postoperative 2.9 ± 0.2 to 3.3 ± 0.2 cm3 at 6 months versus 1.7 ± 0.1 to 1.9 ± 0.2 cm3) and a greater final decrease over 2-5 years postoperatively (from 3.1 ± 0.2 to 1.9 ± 0.2 cm3 versus 1.8 ± 0.2 ± 0.1 to 1.3 ± 0.1 cm3) (P < 0.001). The femoral tunnel volume remained comparable between the two groups throughout the follow-up period, with an initial 1.6 ± 0.1 cm3 in both groups and 1.2 ± 0.1 vs. 1.3 ± 0.1 after 5 years in the screw and button groups, respectively (P ≥ 0.314). The maximum tibial and femoral tunnel diameters were significantly larger with screw fixation at all four time points. Tibial diameters measured 11.1 ± 0.2, 12.3 ± 0.3, 12.3 ± 0.4, and 11.2 ± 0.4 mm in the screw group versus 8.1 ± 0.3, 8.9 ± 0.3, 9.1 ± 0.4 and 8.2 ± 0.5 mm in the button group (P < 0.001). Femoral diameters measured 8.6 ± 0.2, 10.5 ± 0.4, 10.2 ± 0.3, and 8.9 ± 0.3 versus 7.3 ± 0.3, 8.4 ± 0.4, 8.4 ± 0.3, 7.5 ± 0.3, respectively (P ≤ 0.007). Four patients (33%) in the screw group exceeded a diameter of 12 mm on the tibial side after 5 years versus none in the button group (not significant, P = 0.104). Tibial anteroposterior translation measurement with KT-1000 after 5 years was 2.3 ± 2.4 mm in the screw group versus 3.2 ± 3.5 mm in the button group (not significant, P = 0.602). There were no significant differences between the groups in any of the other clinical outcomes.

CONCLUSION

Tibial tunnels in ACLR with screw fixation were associated with a larger increase in tunnel volume within the first 2 years and a greater decrease up to 5 years after surgery, while femoral tunnel volumes did not differ significantly. On the tibial side, the need for staged revision ACLR may be greater after biodegradable interference screw fixation if repeat ruptures occur, especially within the first 2 years after primary ACLR. Concerns may remain regarding a higher graft failure rate with all-inside ACLR.

LEVEL OF EVIDENCE

II.

RCT CONSORT

NCT01755819.

Role of Quadriceps Tendon Autograft in Primary and Revision Anterior Cruciate Ligament Reconstruction

» The quadriceps tendon (QT) autograft is becoming increasingly popular in both primary and revision anterior cruciate ligament reconstruction (ACLR).» The biomechanical properties of the QT are similar to those of the native ACL, the hamstring tendon (HT), and bone-patellar tendon-bone (BTB) autografts.» QT autograft allows surgeons to be flexible with their graft size and reconstruction technique.» The QT autograft performs in a similar fashion to the BTB and HT autografts, with excellent patient-reported outcomes, consistent postoperative knee stability, and low rates of postoperative complications including graft failure and donor site morbidity.» There are emerging data that the QT autograft is a viable option in revision ACLR.

Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction Using a Calcium Phosphate-Hybridized Tendon Graft with More than an Average of 5 Years of Follow-Up: A Follow-Up Study of a Randomized Controlled Trial

Calcium phosphate (CaP)-hybridized tendon grafting using an alternate soaking process improves tendon-to-bone healing in anterior cruciate ligament (ACL) reconstructions. This study aimed to compare bone tunnel enlargement, knee osteoarthritis, and clinical results between CaP-hybridized tendon grafting and conventional grafting in anatomical single-bundle ACL reconstruction. This study was a follow-up of a randomized controlled trial. Between July 2011 and December 2015, 90 patients underwent unilateral anatomical single-bundle ACL reconstructions and were randomly assigned to the CaP-hybridized tendon grafting (CaP group, n = 45; age, 27.1 [14-54] years; sex, 21 males and 24 females) or conventional grafting (control group, n = 45; age, 22.9 [13-58] years; sex, 26 males and 19 females). The randomization was performed according to the days of the week when the patients first visited the outpatient. The CaP-hybridized tendon grafting was created intraoperatively. The tendon grafts were soaked in a calcium solution for 30 s. After that, the tendon grafts were soaked in a NaHPO4 solution for 30 s. This soaking cycle between the calcium solution and the NaHPO4 solution was repeated 10 times. The bone tunnel enlargement, osteoarthritis grade, clinical score, and sports level were evaluated in patients who could be followed up for >3 years (CaP group, n = 20, average follow-up period 6.0 [5.1-6.9] years; control group, n = 15, average follow-up period 5.6 [4.3-6.9] years). Clinical scores, sports levels, and osteoarthritis grades were analyzed using a generalized linear mixed model (GLMM) based on repeated measurement data from preoperative and final observations, with time, group, sex, age, and BMI as fixed effects and the effect of individual differences as variable effects. In addition, bone-tunnel enlargements were analyzed using generalized linear models (GLM) with group, sex, age, and BMI as the main effects. Compared with the control group, the CaP group exhibited significantly reduced bone-tunnel enlargement on the femoral side (anteroposterior diameter; CaP group, 7.9% [-1.1-16.8] vs. control group, 29.2% [17.9-40.5], p = 0.004, MCID 16.05, proximal-distal diameter; CaP group, 7.9% [-1.9-17.8] vs. control group, 22.8% [10.9-34.7], p = 0.062, MCID 15.00). The osteoarthritis grades progressed in both groups (p < 0.001). The clinical scores and sports levels were not significantly different between the groups. This study suggests that the calcium phosphate-hybridized tendon graft reduces femoral bone-tunnel enlargement after anatomical single-bundle anterior cruciate ligament reconstruction in an average >5-year follow-up period. A longer follow-up period is necessary to reveal the clinical effects of the calcium phosphate-hybridized tendon grafts in anterior cruciate ligament reconstruction.

Tibial tunnel enlargement is affected by the tunnel diameter-screw ratio in tibial hybrid fixation for hamstring ACL reconstruction

INTRODUCTION

There is no evidence on screw diameter with regards to tunnel size in anterior cruciate ligament reconstruction (ACLR) using hybrid fixation devices. The hypothesis was that an undersized tunnel coverage by the tibial screw leads to subsequent tunnel enlargement in ACLR in hybrid fixation technique.

METHODS

In a retrospective case series, radiographs and clinical scores of 103 patients who underwent primary hamstring tendon ACLR with a hybrid fixation technique at the tibial site (interference screw and suspensory fixation) were obtained. Tunnel diameters in the frontal and sagittal planes were measured on radiographs 6 weeks and 12 months postoperatively. Tunnel enlargement of more than 10% between the two periods was defined as tunnel widening. Tunnel coverage ratio was calculated as the tunnel diameter covered by the screw in percentage.

RESULTS

Overall, tunnel widening 12 months postoperatively was 23.1 ± 17.1% and 24.2 ± 18.2% in the frontal and sagittal plane, respectively. Linear regression analysis revealed the tunnel coverage ratio to be a negative predicting risk factor for tunnel widening (p = 0.001). The ROC curve analysis provided an ideal cut-off for tunnel enlargement of > 10% at a tunnel coverage ratio of 70% (sensitivity 60%, specificity 81%, AUC 75%, p < 0.001). Patients (n = 53/103) with a tunnel coverage ratio of < 70% showed significantly higher tibial tunnel enlargement of 15% in the frontal and sagittal planes. The binary logistic regression showed a significant OR of 6.9 (p = 0.02) for tunnel widening > 10% in the frontal plane if the tunnel coverage ratio was < 70% (sagittal plane: OR 14.7, p = 0.001). Clinical scores did not correlate to tunnel widening.

CONCLUSION

Tibial tunnel widening was affected by the tunnel diameter coverage ratio. To minimize the likelihood of disadvantageous tunnel expansion-which is of importance in case of revision surgery-an interference screw should not undercut the tunnel diameter by more than 1 mm.

Current trends in graft choice for anterior cruciate ligament reconstruction - part I: anatomy, biomechanics, graft incorporation and fixation

Graft selection in anterior cruciate ligament (ACL) reconstruction is critical, as it remains one of the most easily adjustable factors affecting graft rupture and reoperation rates. Commonly used autografts, including hamstring tendon, quadriceps tendon and bone-patellar-tendon-bone, are reported to be biomechanically equivalent or superior compared to the native ACL. Despite this, such grafts are unable to perfectly replicate the complex anatomical and histological characteristics of the native ACL. While there remains inconclusive evidence as to the superiority of one autograft in terms of graft incorporation and maturity, allografts appear to demonstrate slower incorporation and maturity compared to autografts. Graft fixation also affects graft properties and subsequent outcomes, with each technique having unique advantages and disadvantages that should be carefully considered during graft selection.

Graft-Specific Surgical and Rehabilitation Considerations for Anterior Cruciate Ligament Reconstruction with the Quadriceps Tendon Autograft

Anterior cruciate ligament reconstruction (ACLR) with a bone-patellar tendon-bone (BPTB) or hamstring tendon (HT) autograft has traditionally been the preferred surgical treatment for patients returning to Level 1 sports. More recently, international utilization of the quadriceps tendon (QT) autograft for primary and revision ACLR has increased in popularity. Recent literature suggests that ACLR with the QT may yield less donor site morbidity than the BPTB and better patient-reported outcomes than the HT. Additionally, anatomic and biomechanical studies have highlighted the robust properties of the QT itself, with superior levels of collagen density, length, size, and load-to-failure strength compared to the BPTB. Although previous literature has described rehabilitation considerations for the BPTB and HT autografts, there is less published with respect to the QT. Given the known impact of the various ACLR surgical techniques on postoperative rehabilitation, the purpose of this clinical commentary is to present the procedure-specific surgical and rehabilitation considerations for ACLR with the QT, as well as further highlight the need for procedure-specific rehabilitation strategies after ACLR by comparing the QT to the BPTB and HT autografts.

Level of Evidence

Level 5.

The influence of ruptured scar pattern of human anterior cruciate ligament remnant tissue on tendon-bone healing in vivo

The purpose of this study was to determine whether the transplantation of human cells from a non-reattached injured anterior cruciate ligament (ACL) remnant could enhance tendon-bone healing. Human ACL remnant tissue was classified into two groups based on the morphologic pattern as per Crain's classification: (1) non-reattachment group (Crain Ⅳ) and (2) reattachment group (Crain Ⅰ-Ⅲ). Seventy-five 10-week-old immunodeficient rats underwent ACL reconstruction followed by intracapsular administration of one of the following: (1) ACL-derived cells from the non-reattached remnant (non-reattachment group) (n = 5), (2) ACL-derived cells from the reattached tissue (reattachment group) (n = 5), or (3) phosphate-buffered saline (PBS) only (PBS group) (n = 5). Histological (Weeks 2, 4, and 8), immunohistochemical (Week 2), radiographic (Weeks 0, 2, 4, and 8), and biomechanical (Week 8) assessments were performed. Histological evaluation showed high and early healing, induction of endochondral ossification-like integration, and mature bone ingrowth at Week 4 in the non-reattachment group. Microcomputed tomography at Week 4 showed that the tibial bone tunnels in the non-reattachment group were significantly reduced compared to those in the reattachment and PBS groups. Moreover, biomechanical testing showed that ultimate load-to-failure in the non-reattachment group tended to be larger than that in the reattachment group, though not statistically significant. The enhanced healing potential in the non-reattachment group was explained by the increase in intrinsic angiogenesis/osteogenesis. In the subacute phase, the ACL-derived cells with the non-reattached morphologic pattern showed greater and earlier tendon bone healing compared with the cells obtained from the reattached morphologic pattern.

GLI1 Deficiency Impairs the Tendon-Bone Healing after Anterior Cruciate Ligament Reconstruction: In Vivo Study Using Gli1-Transgenic Mice

Hedgehog (Hh) signaling plays a fundamental role in the enthesis formation process and GLI-Kruppel family member GLI1 (Gli1) is a key downstream mediator. However, the role of Gli1 in tendon-bone healing after anterior cruciate ligament reconstruction (ACLR) is unknown. To evaluate the tendon-bone healing after ACLR in Gli1^LacZ/LacZ (GLI1-NULL) mice, and compare Gli1^LacZ/WT (GLI1-HET) and Gli1^WT/WT wild type (WT) mice, a total of 45 mice, 15 mice each of GLI1-NULL, GLI1-HET and WT were used in this study. All mice underwent microsurgical ACLR at 12 weeks of age. Mice were euthanized at 4 weeks after surgery and were used for biomechanical testing, histological evaluation, and micro-CT analysis. The GLI1-NULL group had significantly lower biomechanical failure force, poorer histological healing, and lower BV/TV when compared with the WT and GLI1-HET groups. These significant differences were only observed at the femoral tunnel. Immunohistology staining showed positive expression of Indian hedgehog (IHH) and Patched 1(PTCH1) in all three groups, which indicated the activation of the Hh signal pathway. The GLI1 was negative in the GLI1-NULL group, validating the absence of GLI1 protein in these mice. These results proved that activation of the Hh signaling pathway occurs during ACL graft healing, and the function of Gli1 was necessary for tendon-bone healing. Healing in the femoral tunnel is more obviously impaired by Gli1 deficiency. Our findings provide further insight into the molecular mechanism of tendon-bone healing and suggest that Gli1 might represent a novel therapeutic target to improve tendon-bone healing after ACLR.

Synergistic Effect of Reverse Drilling and Bone Dust on Femoral Tendon-Bone Healing After Anterior Cruciate Ligament Reconstruction in a Rabbit Model

BACKGROUND

Anterior cruciate ligament (ACL) injuries and bone tunnel enlargement (BTE) after ACL reconstruction (ACLR) remain frequent issues. Bone dust (BD) produced by tunnel preparation with osteogenic ability and reverse drilling (RD), an easy compaction technique, make it accessible to enhance tendon-bone healing in the clinic.

HYPOTHESIS

RD and BD synergistically promote tendon-bone healing by improving peritunnel bone and preventing BTE in femurs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 96 New Zealand White rabbits underwent ACLR. The semitendinosus tendon was freed before medial parapatellar arthrotomy. After the native ACL was transected, bone tunnels were prepared through the footprint of the native ACL. All animals were randomly assigned to 1 of 4 groups according to different tunnel preparation methods: group 1 (irrigation after extraction drilling [ED]; control group), group 2 (irrigation after RD), group 3 (no irrigation after ED), and group 4 (no irrigation after RD). BD was harvested by irrigating tunnels and was characterized by morphology and size. The specimens underwent microarchitectural, histological, and biomechanical evaluations at 4, 8, and 12 weeks postoperatively.

RESULTS

Micro-computed tomography demonstrated more peritunnel bone and less BTE in the femurs of group 4 compared with the other groups. Histologically, BD possessed osteogenic activity in bone tunnels postoperatively. Meanwhile, group 4 regenerated a higher amount of the tendon-bone interface and more peritunnel bone than group 1. Biomechanically, group 4 showed higher failure loads and stiffness than group 1. However, peritunnel bone loss, active osteoclasts, and significant BTE were found in the femurs of group 1 and group 3 at 12 weeks postoperatively, while no strong correlation was found between BTE and inflammatory cytokines. Scanning electron microscopy and particle size analysis suggested that BD produced by ED and RD had no difference in size.

CONCLUSION

Tendon-bone healing was facilitated by the synergistic effect of RD and BD in femurs.

CLINICAL RELEVANCE

This study provides a more accessible and effective surgical strategy to promote tendon-bone healing after ACLR by increasing peritunnel bone and preventing BTE in femurs.

Adjustable-Loop Cortical Suspensory Fixation Results in Greater Tibial Tunnel Widening Compared to Interference Screw Fixation in Primary Anterior Cruciate Ligament Reconstruction

Background: Although the use of adjustable-loop suspensory fixation has increased in recent years, the influence of the shortcomings of suspensory fixation, such as the bungee-cord or windshield-wiper effects, on tunnel widening remains to be clarified. Hypothesis/Purpose: The purpose of this study was to compare adjustable-loop femoral cortical suspensory fixation and interference screw fixation in terms of tunnel widening and clinical outcomes after anterior cruciate ligament reconstruction (ACLR). We hypothesized that tunnel widening in the adjustable-loop femoral cortical suspensory fixation (AL) group would be comparable to that in the interference screw fixation (IF) group. Methods: This study evaluated patients who underwent primary ACLR at our institution between March 2015 and June 2019. The femoral and tibial tunnel diameters were measured using plain radiographs in the immediate postoperative period and 2 years after ACLR. Tunnel widening and clinical outcomes (Lysholm score, 2000 International Knee Documentation Committee subjective score, and Tegner activity level) were compared between the two groups. Results: There were 48 patients (mean age, 29.8 ± 12.0 years) in the AL group and 44 patients (mean age, 26.0 ± 9.5 years) in the IF group. Tunnel widening was significantly greater in the AL group than that in the IF group at the tibia anteroposterior (AP) middle (2.03 mm vs. 1.32 mm, p = 0.017), tibia AP distal (1.52 mm vs. 0.84 mm, p = 0.012), tibia lateral proximal (1.85 mm vs. 1.00 mm, p = 0.001), tibia lateral middle (2.36 mm vs. 1.03 mm, p < 0.001), and tibia lateral distal (2.34 mm vs. 0.85 mm, p < 0.001) levels. There were no significant differences between the two groups with respect to femoral tunnel widening and clinical outcomes. Conclusions: Tibial tunnel widening was significantly greater in the AL group than in the IF group at 2 years after primary ACLR. However, the clinical outcomes in the two groups were comparable at 2 years.

Ligamentization of the reconstructed ACL differs between the intraarticular and intraosseous regions: A quantitative assessment using UTE-T2* mapping

Background

The purpose of this study was to prospectively observe the trends of ultrashort echo time (UTE)-T2* values for the intraarticular and intraosseous regions of reconstructed anterior cruciate ligaments from 6 to 12 months after anterior cruciate ligament reconstruction by using UTE-T2* mapping, and to investigate the changes and differences over time in each region.

Methods

Ten patients underwent UTE-T2* mapping of the operated knee at 6, 9, and 12 months after anterior cruciate ligament reconstruction. The UTE-T2* values of intraarticular and intraosseous regions of reconstructed anterior cruciate ligaments at 6, 9, and 12 months postoperatively were statistically compared.

Results

The UTE-T2* values of the intraarticular region at 6 months postoperatively were significantly higher than those at 9 and 12 months. There were no significant differences in the UTE-T2* values at 6, 9, and 12 months postoperatively in the intraosseous region. At 6 months postoperatively, the UTE-T2* values of the intraarticular region were significantly higher than those of the intraosseous region. The UTE-T2* values of the intraosseous region at the tibia were significantly lower than those of the other sites at any postoperative time point.

Conclusions

According to UTE-T2*mapping-based findings, histological maturation of reconstructed ACLs is faster in the intraosseous region than in the intraarticular region. In particular, the intraarticular region is still undergoing rapid histologic changes at 6 months postoperatively, and its tissue structure is less substantial than normal. The findings of this study may provide clues to determine the optimal timing for safe return to sports in terms of ligamentaization of reconstructed ACLs.

Descriptive Characteristics and Outcomes of Patients Undergoing Revision Anterior Cruciate Ligament Reconstruction With and Without Tunnel Bone Grafting

BACKGROUND

Lytic or malpositioned tunnels may require bone grafting during revision anterior cruciate ligament reconstruction (rACLR) surgery. Patient characteristics and effects of grafting on outcomes after rACLR are not well described.

PURPOSE

To describe preoperative characteristics, intraoperative findings, and 2-year outcomes for patients with rACLR undergoing bone grafting procedures compared with patients with rACLR without grafting.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 1234 patients who underwent rACLR were prospectively enrolled between 2006 and 2011. Baseline revision and 2-year characteristics, surgical technique, pathology, treatment, and patient-reported outcome instruments (International Knee Documentation Committee [IKDC], Knee injury and Osteoarthritis Outcome Score [KOOS], Western Ontario and McMaster Universities Osteoarthritis Index, and Marx Activity Rating Scale [Marx]) were collected, as well as subsequent surgery information, if applicable. The chi-square and analysis of variance tests were used to compare group characteristics.

RESULTS

A total of 159 patients (13%) underwent tunnel grafting-64 (5%) patients underwent 1-stage and 95 (8%) underwent 2-stage grafting. Grafting was isolated to the femur in 31 (2.5%) patients, the tibia in 40 (3%) patients, and combined in 88 patients (7%). Baseline KOOS Quality of Life (QoL) and Marx activity scores were significantly lower in the 2-stage group compared with the no bone grafting group (P≤ .001). Patients who required 2-stage grafting had more previous ACLRs (P < .001) and were less likely to have received a bone-patellar tendon-bone or a soft tissue autograft at primary ACLR procedure (P≤ .021) compared with the no bone grafting group. For current rACLR, patients undergoing either 1-stage or 2-stage bone grafting were more likely to receive a bone-patellar tendon-bone allograft (P≤ .008) and less likely to receive a soft tissue autograft (P≤ .003) compared with the no bone grafting group. At 2-year follow-up of 1052 (85%) patients, we found inferior outcomes in the 2-stage bone grafting group (IKDC score = 68; KOOS QoL score = 44; KOOS Sport/Recreation score = 65; and Marx activity score = 3) compared with the no bone grafting group (IKDC score = 77; KOOS QoL score = 63; KOOS Sport/Recreation score = 75; and Marx activity score = 7) (P≤ .01). The 1-stage bone graft group did not significantly differ compared with the no bone grafting group.

CONCLUSION

Tunnel bone grafting was performed in 13% of our rACLR cohort, with 8% undergoing 2-stage surgery. Patients treated with 2-stage grafting had inferior baseline and 2-year patient-reported outcomes and activity levels compared with patients not undergoing bone grafting. Patients treated with 1-stage grafting had similar baseline and 2-year patient-reported outcomes and activity levels compared with patients not undergoing bone grafting.

Evaluation of Tibial Fixation Devices for Quadrupled Hamstring ACL Reconstruction

Background:

Shortcomings to tibial-side fixation have been reported as causes of failure after anterior cruciate ligament reconstruction. Adjustable-loop suspensory devices have become popular; however, no comparison with hybrid fixation (ie, interference screw and cortical button) exists to our knowledge.

Purpose:

The purpose of this study was to compare the biomechanical properties of adjustable loop devices (ALDs) in full-tunnel and closed-socket configurations in relation to hybrid fixation. We hypothesized that primary stability of fixation by a tibial ALD will not be inferior to hybrid fixation.

Study Design:

Controlled laboratory study.

Methods:

Tibial fixation of a quadrupled tendon graft was biomechanically investigated in a porcine tibia–bovine tendon model using 5 techniques (n = 6 specimens each). The tested constructs included hybrid fixation with a cortical fixation button and interference screw (group 1), single cortical fixation with the full-tunnel technique using an open-suture strand button (group 2) or an ALD (group 3), or closed-socket fixation using 2 different types of ALDs (groups 4 and 5). Each specimen was evaluated using a materials testing machine (1000 cycles from 50-250 N and pull to failure). Force at failure, cyclic displacement, stiffness, and ability to pretension the graft during insertion were compared among the groups.

Results:

No differences in ultimate load to failure were found between the ALD constructs (groups 3, 4, and 5) and hybrid fixation (group 1). Cyclic displacement was significantly higher in group 2 vs all other groups (P < .001); however, no difference was observed in groups 3, 4, and 5 as compared with group 1. The remaining tension on the construct after fixation was significantly higher in groups 3 and 4 vs groups 1, 2, and 5 (P < .02 for all comparisons), irrespective of whether a full-tunnel or closed-socket approach was used.

Conclusion:

Tibial anterior cruciate ligament graft fixation with knotless ALDs achieved comparable results with hybrid fixation in the full-tunnel and closed-socket techniques. The retention of graft tension appears to be biomechanically more relevant than tunnel type.

Clinical Relevance:

The study findings emphasize the importance of the tension at which fixation is performed.

Distinct inflammatory macrophage populations sequentially infiltrate bone‐to‐tendon interface tissue after ACL reconstruction surgery in mice

Macrophages are important for repair of injured tissues, but their role in healing after surgical repair of musculoskeletal tissues is not well understood. We used single‐cell RNA sequencing (RNA‐seq), flow cytometry, and transcriptomics to characterize functional phenotypes of macrophages in a mouse anterior cruciate ligament reconstruction (ACLR) model that involves bone injury followed by a healing phase of bone and fibrovascular interface tissue formation that results in bone‐to‐tendon attachment. We identified a novel “surgery‐induced” highly inflammatory CD9+ IL1+ macrophage population that expresses neutrophil‐related genes, peaks 1 day after surgery, and slowly resolves while transitioning to a more homeostatic phenotype. In contrast, CX3CR1+ CCR2+ macrophages accumulated more slowly and unexpectedly expressed an interferon signature, which can suppress bone formation. Deletion of Ccr2 resulted in an increased amount of bone in the surgical bone tunnel at the tendon interface, suggestive of improved healing. The “surgery‐induced macrophages” identify a new cell type in the early phase of inflammation related to bone injury, which in other tissues is dominated by blood‐derived neutrophils. The complex patterns of macrophage and inflammatory pathway activation after ACLR set the stage for developing therapeutic strategies to target specific cell populations and inflammatory pathways to improve surgical outcomes. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Tackling the Challenges of Graft Healing After Anterior Cruciate Ligament Reconstruction-Thinking From the Endpoint

Anterior cruciate ligament (ACL) tear is common in sports and accidents, and accounts for over 50% of all knee injuries. ACL reconstruction (ACLR) is commonly indicated to restore the knee stability, prevent anterior–posterior translation, and reduce the risk of developing post-traumatic osteoarthritis. However, the outcome of biological graft healing is not satisfactory with graft failure after ACLR. Tendon graft-to-bone tunnel healing and graft mid-substance remodeling are two key challenges of biological graft healing after ACLR. Mounting evidence supports excessive inflammation due to ACL injury and ACLR, and tendon graft-to-bone tunnel motion negatively influences these two key processes. To tackle the problem of biological graft healing, we believe that an inductive approach should be adopted, starting from the endpoint that we expected after ACLR, even though the results may not be achievable at present, followed by developing clinically practical strategies to achieve this ultimate goal. We believe that mineralization of tunnel graft and ligamentization of graft mid-substance to restore the ultrastructure and anatomy of the original ACL are the ultimate targets of ACLR. Hence, strategies that are osteoinductive, angiogenic, or anti-inflammatory should drive graft healing toward the targets. This paper reviews pre-clinical and clinical literature supporting this claim and the role of inflammation in negatively influencing graft healing. The practical considerations when developing a biological therapy to promote ACLR for future clinical translation are also discussed.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model

BACKGROUND

Anterior cruciate ligament (ACL) repair techniques are new emerging strategies prevailing, in selected cases, over standard reconstruction of the ACL with excision of its remnants. Mid-substance ACL tears represent a challenge for ACL repair techniques, and remnants-preserving ACL reconstruction (rp-ACLR) using an autograft remains the recommended treatment in this situation. However, morbidity associated with the autograft harvesting prompts the need for alternative surgical strategies based on the use of synthetic scaffolds. Relevant small animal models of mid-substance tears with ACL remnants preservation and reconstruction are necessary to establish the preliminary proof of concept of these new strategies.

METHODS

A rat model of rp-ACLR using a tendinous autograft after complete mid-substance ACL transection was established. Twelve weeks following surgery, clinical outcomes and knee joints were assessed through visual gait analysis, Lachman tests, thigh perimeter measurements, magnetic resonance imaging, micro-computed tomography, and histology, to evaluate the morbidity of the procedure, accuracy of bone tunnel positioning, ACL remnants fate, osteoarthritis, and autograft bony integration. Results were compared with those obtained with isolated ACL transection without reconstruction and to right non-operated knees.

RESULTS AND DISCUSSION

Most operated animals were weight-bearing the day following surgery, and no adverse inflammatory reaction has been observed for the whole duration of the study. Autograft fixation with cortical screws provided effective graft anchorage until sacrifice. Healing of the transected ACL was not observed in the animals in which no graft reconstruction was performed. rp-ACLR was associated with a reduced degeneration of the ACL remnants (p = 0.004) and cartilages (p = 0.0437). Joint effusion and synovitis were significantly lower in the reconstructed group compared to the transected ACL group (p = 0.004). Most of the bone tunnel apertures were anatomically positioned in the coronal and/or sagittal plane. The most deviated bone tunnel apertures were the tibial ones, located in median less than 1 mm posteriorly to anatomical ACL footprint center.

CONCLUSION

This study presents a cost-effective, new relevant and objective rat model associated with low morbidity for the preliminary study of bio-implantable materials designed for remnants-preserving ACL surgery after mid-substance ACL tear.

An Anatomically Placed Tibial Tunnel does not Completely Surround a Simulated PCL Reconstruction Graft in the Proximal Tibia

INTRODUCTION

 It is hypothesized that anatomic tunnel placement will create tunnels with violation of the posterior cortex and subsequently an oblique aperture that is not circumferentially surrounded by bone. In this article, we aimed to characterize posterior cruciate ligament (PCL) tibial tunnel using a three-dimensional (3D) computed tomography (CT) model.

METHODS

 Ten normal knee CTs with the patella, femur, and fibula removed were used. Simulated 11 mm PCL tibial tunnels were created at 55, 50, 45, and 40 degrees. The morphology of the posterior proximal tibial exit was examined with 3D modeling software. The length of tunnel not circumferentially covered (cortex violation) was measured to where the tibial tunnel became circumferential. The surface area and volume of the cylinder both in contact with the tibial bone and that not in contact with the tibia were determined. The percentages of the stick-out length surface area and volume not in contact with bone were calculated.

RESULTS

 The mean stick-out length of uncovered graft at 55, 50, 45, and 40 degrees were 26.3, 20.5, 17.3, and 12.7 mm, respectively. The mean volume of exposed graft at 55, 50, 45, and 40 degrees were 840.8, 596.2, 425.6, and 302.9 mm³, respectively. The mean percent of volume of exposed graft at 55, 50, 45, and 40 degrees were 32, 29, 25, and 24%, respectively. The mean surface of exposed graft at 55, 50, 45, and 40 degrees were 372.2, 280.4, 208.8, and 153.3 mm², respectively. The mean percent of surface area of exposed graft at 55, 50, 45, and 40 degrees were 40, 39, 34, and 34%, respectively.

CONCLUSION

 Anatomic tibial tunnel creation using standard transtibial PCL reconstruction techniques consistently risks posterior tibial cortex violation and creation of an oblique aperture posteriorly. This risk is decreased with decreasing the angle of the tibial tunnel, though the posterior cortex is still compromised with angles as low as 40 degrees. With posterior cortex violation, a surgeon should be aware that a graft within the tunnel or socket posteriorly may not be fully in contact with bone. This is especially relevant with inlay and socket techniques.

Two-Stage Revision Anterior Cruciate Ligament Reconstruction with Cannulated Allograft Bone Dowels Soaked in Bone Marrow Aspirate Concentrate

Anterior cruciate ligament reconstruction (ACLR) is one of the most common orthopedic procedures performed each year. The majority of patients undergoing these reconstructions will experience long-term stability and symptomatic relief; however, some will require a revision ACLR procedure. In general, revision ACLRs are more challenging than primary ACLRs due to several diagnostic and technical considerations. A revision ACLR can be performed with either a one-stage or two-stage procedure, which is based on the presence or absence of malpositioned tunnels, bone loss, and tunnel expansion. Recently, the introduction of preshaped allograft bone dowels as a bone grafting option has gained popularity. They provide immediate structural stability and avoid donor site morbidity associated with autografts. The purpose of this article is to outline a bone-grafting tunnel technique with cannulated allograft bone dowels soaked in bone marrow aspirate concentrate (BMAC) used in the first stage of a staged revision ACLR procedure.

Differences in artificial ligament graft osseointegration of the anterior cruciate ligament in a sheep model: a comparison between interference screw and cortical suspensory fixation

Background

Interference screws are the most common femoral fixation for anterior cruciate ligament (ACL) reconstruction with polyethylene terephthalate (PET) artificial ligaments. However, interference screws have several disadvantages, such as the risk of one tunnel blowout and damage to the graft. Suspensory fixations have the advantages of high tensile strength and promotion of graft bone contact. The purpose of this study was to compare PET artificial ligament graft osseointegration between interference screw fixation (ISF) and cortical suspensory fixation (CSF) for ACL reconstruction.

Methods

Forty sheep underwent ACL reconstruction of the right knee with PET artificial ligament. The graft was fixed with ISF or CSF for femoral fixation. Animals were randomly assigned to the ISF (n=20) or the CSF (n=20) groups. The sheep were sacrificed at 3 or 12 months postoperatively for biomechanical tests, micro computed tomography (micro-CT) scans, and histological assessments.

Results

The mean load-to-failure between the CSF group (836±355 N) appeared higher than that of the ISF group (604±277 N) at 3 months, but no significant difference was detected between the groups (P=0.24). At 12 months, there was also no significant difference in load-to-failure between the CSF and ISF groups (1,194±350 vs. 1,097±764 N; P=0.78). According to the micro-CT scan results, the femoral bone tunnel diameter of the ISF group appeared larger than that of the CSF group at 3 months (12±1 vs. 10±1 mm; P=0.02) and similar to that of the CSF group at 12 months (12±1 vs. 11±2 mm; P=0.38). Furthermore, histological results showed that at the graft-tunnel interface of the femoral tunnel aperture, disoriented fibers formed in the ISF group while oriented and dense fibers formed in the CSF group.

Conclusions

ACLR with synthetic ligament by cortical suspension devices with adjustable loops demonstrated a better graft-bone healing capacity at the femoral tunnel aperture compared with that from titanium interference screws over 12 months postoperatively. No significant difference was found in biomechanical strength between the two fixation methods during the early healing stage.

Effects of and Response to Mechanical Loading on the Knee

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Effect of Demineralized Bone Matrix, Bone Marrow Mesenchymal Stromal Cells, and Platelet-Rich Plasma on Bone Tunnel Healing After Anterior Cruciate Ligament Reconstruction: A Comparative Micro-Computed Tomography Study in a Tendon Allograft Sheep Model

Background:

The effect of demineralized bone matrix (DBM), bone marrow–derived mesenchymal stromal cells (BMSCs), and platelet-rich plasma (PRP) on bone tunnel healing in anterior cruciate ligament reconstruction (ACLR) has not been comparatively assessed.

Hypothesis:

These orthobiologics would reduce tunnel widening, and the effects on tunnel diameter would be correlated with tunnel wall sclerosis.

Study Design:

Controlled laboratory study.

Methods:

A total of 20 sheep underwent unilateral ACLR using tendon allograft and outside-in interference screw fixation. The animals were randomized into 4 groups (n = 5 per group): Group 1 received 4mL of DBM paste, group 2 received 10 million BMSCs in fibrin sealant, group 3 received 12 mL of activated leukocyte-poor platelet-rich plasma, and group 4 (control) received no treatment. The sheep were euthanized after 12 weeks, and micro-computed tomography scans were performed. The femoral and tibial tunnels were divided into thirds (aperture, midportion, and exit), and the trabecular bone structure, bone mineral density (BMD), and tunnel diameter were measured. Tunnel sclerosis was defined by a higher bone volume in a 250-µm volume of interest compared with a 4-mm volume of interest surrounding the tunnel.

Results:

Compared with the controls, the DBM group had a significantly higher bone volume fraction (bone volume/total volume [BV/TV]) (52.7% vs 31.8%; P = .020) and BMD (0.55 vs 0.47 g/cm³; P = .008) at the femoral aperture and significantly higher BV/TV at femoral midportion (44.2% vs 32.9%; P = .038). There were no significant differences between the PRP and BMSC groups versus controls in terms of trabecular bone analysis or BMD. In the controls, widening at the femoral tunnel aperture was significantly greater than at the midportion (46.7 vs 41.7 mm²; P = .034). Sclerosis of the tunnel was common and most often seen at the femoral aperture. In the midportion of the femoral tunnel, BV/TV (r = 0.52; P = .019) and trabecular number (r_S = 0.50; P = .024) were positively correlated with tunnel widening.

Conclusion:

Only DBM led to a significant increase in bone volume, which was seen in the femoral tunnel aperture and midportion. No treatment significantly reduced bone tunnel widening. Tunnel sclerosis in the femoral tunnel midportion was correlated significantly with tunnel widening.

Clinical Relevance:

DBM might have potential clinical use to enhance healing in the femoral tunnel after ACLR.

The Graft Insertion Length in the Femoral Tunnel During Anterior Cruciate Ligament Reconstruction With Suspensory Fixation and Tibialis Anterior Allograft Does Not Affect Surgical Outcomes but Is Negatively Correlated With Tunnel Widening

PURPOSE

To investigate the surgical outcomes of anterior cruciate ligament (ACL) reconstruction using a low-dose irradiated tibialis anterior allograft with a fixed-loop cortical suspension device for the femur based on the graft insertion length (GIL) in the femoral tunnel.

METHODS

Between January 2010 and January 2018, the medical records of consecutive patients who underwent arthroscopic ACL reconstruction with a tibialis anterior allograft fixed with the EndoButton CL for the femur and who had at least 2 years of follow-up were retrospectively evaluated. Patients were classified into 3 groups based on the GIL in the femoral tunnel (group 1, GIL < 15 mm; group 2, GIL of 15-20 mm; and group 3, GIL > 20 mm), and their functional scores, knee laxity, and radiographic parameters were evaluated.

RESULTS

A total of 91 patients were analyzed. There were no statistically significant differences in the functional scores and knee laxity between the 3 groups at 2 years postoperatively. However, significant differences were observed in tunnel widening at 1 year postoperatively in the femur (P = .045 for absolute value and P = .004 for relative value) and the tibia (P = .014 for absolute value and P = .012 for relative value), revealing that both the femoral and tibial tunnels widened as the GIL decreased. Additional linear regression analyses were performed to identify whether the GIL independently affects tunnel widening. Consequently, the femoral tunnel depth, tunnel diameter, and GIL were found to independently influence femoral tunnel widening (P = .008, P = .019, and P < .001, respectively), whereas the tunnel diameter and GIL affected tibial tunnel widening (P < .001 and P = .004, respectively).

CONCLUSIONS

The GIL in the femoral tunnel during ACL reconstruction using a tibialis anterior allograft with a fixed-loop cortical suspension device for the femur has no significant association with the postoperative functional outcomes and knee laxity, but it has a negative correlation with tunnel widening in the femur and the tibia.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Biomechanical analysis of three different types of fixators for anterior cruciate ligament reconstruction via finite element method: a patient-specific study

Complication rates of anterior cruciate ligament reconstruction (ACL-R) were reported to be around 15% although it is a common arthroscopic procedure with good outcomes. Breakage and migration of fixators are still possible even months after surgery. A fixator with optimum stability can minimise those two complications. Factors that affect the stability of a fixator are its configuration, material, and design. Thus, this paper aims to analyse the biomechanical effects of different types of fixators (cross-pin, interference screw, and cortical button) towards the stability of the knee joint after ACL-R. In this study, finite element modelling and analyses of a knee joint attached with double semitendinosus graft and fixators were carried out. Mimics and 3-Matic softwares were used in the development of the knee joint models. Meanwhile, the graft and fixators were designed by using SolidWorks software. Once the meshes of all models were finished in 3-Matic, simulation of the configurations was done using MSC Marc Mentat software. A 100-N anterior tibial load was applied onto the tibia to simulate the anterior drawer test. Based on the findings, cross-pin was found to have optimum stability in terms of stress and strain at the femoral fixation site for better treatment of ACL-R.

The Effect of Antiosteoporosis Therapy With Risedronate on Rotator Cuff Healing in an Osteoporotic Rat Model

BACKGROUND

Osteoporosis increases the revision rate of rotator cuff repair (RCR). Weak fixation might not be the only cause of high RCR failure rates. The biological mechanism associated with tendon-to-bone healing after RCR in osteoporosis should be investigated.

HYPOTHESIS

(1) Osteoporosis would impair rotator cuff healing through the high osteoclastic activity at the repaired interface. (2) Risedronate would promote rotator cuff healing by reducing osteoclastic activity at the repaired interface.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 84 female Sprague Dawley rats were randomly treated using ovariectomy or sham surgeries to establish osteoporotic and nonosteoporotic rat models. After confirming osteoporosis, a chronic rotator cuff tear model was created and RCR was performed. Postoperatively, osteoporotic rats were randomly divided into osteoporosis (OP) and osteoporosis with risedronate administration (OP+RIS) groups. Nonosteoporotic rats were used as the control (CON) group. Osteoclastic activity was measured at 1 and 3 weeks after RCR, and histologic analysis of the tendon-to-bone interface, bone morphometric evaluation, and biomechanical tests were performed at 4 and 8 weeks.

RESULTS

At the early healing stages of 1 and 3 weeks after RCR, the OP group showed the highest osteoclast density at the repaired interface. Compared with the OP group, risedronate administration significantly decreased osteoclast density in the OP+RIS group. At 8 weeks, histologic scores were greater in the OP+RIS group than in the OP group but still lower than in the CON group. Histologic scores at 8 weeks were negatively correlated with osteoclast density at the early healing stage. Additionally, the OP+RIS group showed better bone morphometric parameters and biomechanical properties than did the OP group.

CONCLUSION

Osteoporosis impaired rotator cuff healing, which might be related to the high osteoclast density at the repaired interface at the early healing stage. Postoperative risedronate administration decreased osteoclast density and enhanced rotator cuff healing in osteoporotic rats, although the effect was inferior to that in nonosteoporotic rats.

CLINICAL RELEVANCE

Postoperative risedronate administration can be considered a potential therapy to enhance rotator cuff healing in patients with postmenopausal osteoporosis. However, this needs to be verified in a clinical setting.

Femoral Tunnel Widening Via Transcondylar Cross-Pin Fixation Versus Extracortical Suspensory Fixation After Single-Bundle ACLR: A Systematic Review and Meta-analysis

Background:

Compared with extracortical suspensory fixation, the close-to-joint transcondylar cross-pin fixation method in anterior cruciate ligament reconstruction (ACLR) is believed to entail less intratunnel graft motion and subsequently lead to less tunnel widening.

Purpose:

To assess femoral tunnel widening via the transcondylar cross-pin method or the suspensory femoral fixation method in patients who had undergone ACLR.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

This review focused on studies on femoral-tunnel widening after single-bundle ACLR with cross-pin (Rigidfix or Transfix) and/or Endobutton closed loop (CL). Two reviewers independently recorded data from each study, including the sample size and magnitude of tunnel widening after ACLR.

Results:

Overall, 19 studies were included in this meta-analysis. There was no significant difference between cross-pin and Endobutton CL fixations in the pooled absolute change in tunnel widening from the immediate postoperative period to the final follow-up; this was true at both the tunnel aperture (2.48 mm [95% CI, 1.76-3.2 mm] vs 2.93 mm [95% CI, 1.73-4.13 mm], respectively; P = .527) and the midpoint of the femoral tunnel (2.43 mm [95% CI, 1.77-3.1 mm] vs 2.54 mm [95% CI, –0.33 to 5.42 mm], respectively; P = .937). No significant difference was found in the relative percentage of femoral-tunnel widening between the 2 fixation methods (cross-pin, 43.3% [95% CI, 25.8%-60.8%] vs Endobutton CL, 42.0% [95% CI, 34.1%-49.9%]; P = .965).

Conclusion:

No significant difference in femoral tunnel widening was found to be associated with the use of either cross-pin or extracortical suspensory fixation in patients who underwent single-bundle ACLR.

The Effects of Tensioning of the Anterior Cruciate Ligament Graft on Healing after Soft Tissue Reconstruction

The purpose of this study is to determine the effect of the magnitude of static mechanical tension on the anterior cruciate ligament (ACL) graft at the time of surgery on healing within the graft tunnels. Ninety male rats underwent unilateral ACL resection followed by reconstruction with a soft tissue tendon autograft. The ACL graft mechanical environment was modulated by different ACL graft pretension levels at the time of surgery (no pretension: 0N; moderate tension: 5N; over tension: 10N). External fixators were used to eliminate graft and joint motion during cage activity. Graft-tunnel healing was assessed at 3- and 6-week postoperatively, and articular joint surfaces were assessed at 9 weeks. Our results demonstrate that the ACL graft-tunnel healing was sensitive to different static graft pretension levels as demonstrated by different load-to-failure and stiffness properties among the different pretension levels. Pretensioning the graft to 5N (7-8% of the rat ACL ultimate load to failure) resulted in the best graft-tunnel healing as shown by higher graft-tunnel failure load and stiffness. Higher bone volume fraction was also seen in the 5N group relative to other pretension levels. Histological analysis of the graft-tunnel interface revealed differences in cellularity of the ACL graft between the 5N group and the other two groups. Furthermore, the highest graft pretension level (10N) resulted in loss of proteoglycan content among articular joint surfaces. In conclusion, we found that ACL graft-tunnel healing is sensitive to the magnitude of graft pretension at the time of surgery in a preclinical model of ACL reconstruction with joint immobilization. The combination of high-graft tension and immobilization is also deleterious for the articular surface. Further study is necessary to understand the interaction between the magnitude of graft tensioning and joint motion.

Dual fluoroscopic imaging and CT-based finite element modelling to estimate forces and stresses of grafts in anatomical single-bundle ACL reconstruction with different femoral tunnels

PURPOSE

Little is known about the in vivo forces and stresses on grafts used in anterior cruciate ligament (ACL) reconstruction. The aims of this study were to evaluate and compare the forces and stresses on grafts used in anatomical single-bundle ACL reconstruction at different locations of the femoral footprint (anterior vs middle vs posterior; high vs middle vs low) during a lunge motion.

METHODS

Establish subject-specific finite element models with different graft's tunnel loci to represent the primary ACL reconstructions. A displacement controlled finite element method was used to simulate lunge motions (full extension to ~ 100° of flexion) with six-degree-of-freedom knee kinematics data obtained from the validated dual fluoroscopic imaging techniques. The reaction force of the femur and maximal principal stresses of the grafts were subsequently calculated during knee flexion.

RESULTS

Increased and decreased graft forces were observed when the grafts were located higher and lower on the femoral footprint, respectively; anterior and posterior graft placement did not significantly affect the graft force. Lower and posterior graft placement resulted in less stress on the graft at higher degrees of flexion; there were no significant differences in stress when the grafts were placed from 0° to 30° of flexion on the femoral footprint.

CONCLUSION

The proposed method is able to simulate knee joint motion based on in vivo kinematics. The results demonstrate that posterior to the centre of the femoral footprint is the strategic location for graft placement, and this placement results in anatomical graft behaviour with a low stress state.

Intraarticular Allogenic Mesenchymal Stem Cells and Vascular Endothelial Growth Factor Injection in Anterior Cruciate Ligament Reconstruction

Graft tunnel healing is important for the successful reconstruction of the anterior cruciate ligament by using the hamstring tendon autograft. There are studies that intra graft tunnel Bone Marrow Mesenchymal stem cells (BMSCs) or intra graft tunnel Vascular endothelial growth factor (VEGF) accelerated graft tunnel healing. This study aimed to investigate the effect of using BMSCs+VEGF injected intra-articular on graft tunnel healing. We reconstructed the anterior cruciate ligament (ACL) of 12 rabbits using an autograft hamstring tendon with and without intra-articular BMSCs+VEGF. Histological evaluation was done at 3 and 6 weeks after ACL reconstruction. On the surface between the graft and the bone tunnel obtained collagen fiber thickness or Sharpey fiber is significantly more than the control group (p< 0.05) in the evaluation of 3 weeks and 6 weeks either side of the tibia and the femur. To evaluate the progression of the treatment, treatment group and control group gained progression had significantly when compared to 3 weeks and 6 weeks. It can be concluded that intra-articular injection of VEGF+BMSCs can accelerate the integration of the graft tunnel from histology evaluation on 3 and 6 weeks.

Glenoid bone resorption after Bankart repair: finite element analysis of postoperative stress distribution of the glenoid

BACKGROUND

There are various modifications of the Bankart repair, and postoperative changes to the glenoid morphology after the repair are reported. Among the various procedures performed, a decrease in the lateral glenoid diameter might be related to the surgery that involves removal of the articular cartilage and repair of the labrum-anterior inferior glenohumeral ligament complex on the glenoid surface. This is in contrast to cases without significant bony Bankart lesions that are not on the edge of the glenoid. Thus, this study aimed to compare glenoid rim stress after Bankart repair using 2 methods of finite element analysis: a method of removing the anteroinferior cartilage and repairing the glenohumeral ligament complex on the glenoid and a method of preserving the cartilage and repairing the glenohumeral ligament complex on the glenoid edge.

METHODS

Five preoperative computed tomography scans of patients with traumatic anterior instability who underwent arthroscopic Bankart repair were used. Two models simulating different surgical procedures were created as follows: in model G, a 5-mm-thick cartilage on the glenoid rim was removed between 2 and 7 o'clock, and the glenohumeral ligament complex was repaired on the medial edge of the glenoid bone where the cartilage was removed. In model E, the cartilage on the glenoid rim was not removed, and the glenohumeral ligament complex was repaired on the glenoid edge. The load stresses on the anteroinferior area of the glenoid after Bankart repair with models G and E were measured using finite element analysis.

RESULTS

The stress on the glenoid at 3-4 o'clock was 3.16 MPa in model G and 6.42 MPa in model E (P = .043). The stress at 4-5 o'clock was 1.68 MPa in model G and 4.53 MPa in model E (P = .043). The stress at 5-6 o'clock was 2.26 MPa in model G and 3.93 MPa in model E (P = .043).

CONCLUSION

Significantly lower load stresses were observed at the anteroinferior rim of the glenoid in model G than in model E.

Biomaterials developed for facilitating healing outcome after anterior cruciate ligament reconstruction: Efficacy, surgical protocols, and assessments using preclinical animal models

Anterior cruciate ligament (ACL) reconstruction is the recommended treatment for ACL tear in the American Academy of Orthopaedic Surgeons (AAOS) guideline. However, not a small number of cases failed because of the tunnel bone resorption, unsatisfactory bone-tendon integration, and graft degeneration. The biomaterials developed and designed for improving ACL reconstruction have been investigated for decades. According to the Food and Drug Administration (FDA) and the International Organization for Standardization (ISO) regulations, animal studies should be performed to prove the safety and bioeffect of materials before clinical trials. In this review, we first evaluated available biomaterials that can enhance the healing outcome after ACL reconstruction in animals and then discussed the animal models and assessments for testing applied materials. Furthermore, we identified the relevance and knowledge gaps between animal experimental studies and clinical expectations. Critical analyses and suggestions for future research were also provided to design the animal study connecting basic research and requirements for future clinical translation.

Online Videos Provide Poor Information Quality, Reliability, and Accuracy Regarding Rehabilitation and Return to Sport After Anterior Cruciate Ligament Reconstruction

PURPOSE

To investigate the information quality available on YouTube regarding rehabilitation and return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR).

METHODS

By use of The Onion Router software and predefined search terms, 140 YouTube videos regarding rehabilitation and RTS after ACLR were systematically included. Three scoring systems were used to analyze the included videos: (1) Journal of the American Medical Association (JAMA) benchmark criteria; (2) Global Quality Score (GQS); and (3) self-developed scores for rehabilitation after ACLR and RTS after ACLR, following American Academy of Orthopaedic Surgeons guidelines and current evidence.

RESULTS

The vast majority of the included videos offered poor information quality, reliability, and accuracy. Videos that were uploaded by medically trained professionals showed significantly higher information quality regarding rehabilitation (P = .006 for JAMA score, P < .001 for GQS, and P = .001 for rehabilitation score) and regarding RTS (P < .001 for JAMA score, P < .001 for GQS, and P < .001 for RTS score) compared with commercial videos or personal-testimony videos. Multivariate linear regression also revealed medically trained professionals as significant predictors of higher information quality regarding rehabilitation (β = 0.496 [P < .001] for JAMA score, β = 1.3 [P < .001] for GQS, and β = 3.7 [P < .001] for rehabilitation score) and RTS (β = 0.754 [P < .001] for JAMA score, β = 1.3 [P < .001] for GQS, and β = 5.3 [P < .001] for RTS score).

CONCLUSIONS

The average information quality, reliability, and accuracy of YouTube videos regarding rehabilitation and RTS after ACLR are poor. The information quality of related YouTube videos from medically trained professionals is significantly higher compared with commercial videos or personal-testimony videos.

CLINICAL RELEVANCE

Current YouTube videos regarding rehabilitation and RTS after ACLR do not meet the necessary quality standards. Physicians should also be able to provide alternative sources of high-quality information.

The effect of soft tissue interposition of the Endobutton on clinical results and on its postoperative migration after single-bundle anterior cruciate ligament reconstruction

BACKGROUND

This study aimed to investigate the possible consequences of soft tissue interposition of Endobutton on clinical outcomes and reoperation rates after anterior cruciate ligament reconstruction.

METHODS

We measured the distance between the centre of the Endobutton and the lateral femoral cortex on the postoperative first day anteroposterior X-rays of the 156 knees that underwent anterior cruciate ligament reconstruction. Those with a distance less than 1 mm were regarded as Group 1 (118 patients), the ones between 1 mm and 2 mm were regarded as Group 2 (30 patients) and the ones more than 2 mm were regarded as Group 3 (8 patients). The movement of the Endobutton of more than 1 mm along the femoral tunnel axis on anteroposterior X-rays or its rotation by more than 5° on lateral X-rays during follow-up were considered migration. Clinical assessment scores (Lysholm, Tegner Activity Scale), clinical examination tests, and rates of Endobutton migration in the groups were analysed.

RESULTS

Eleven Endobuttons (9.3%) in Group 1, 26 Endobuttons (86.7%) in Group 2 and all of the 8 Endobuttons (100%) in Group 3 were observed to have migrated. Clinical results and examination tests showed no significant difference between Groups 1 and 2, whereas a significant difference was detected in Group 3 compared to Groups 1 and 2 (p < 0.05).

CONCLUSION

Soft tissue interposition is a major cause of Endobutton migration, and an interposition over 2 mm between the Endobutton and the lateral femoral cortex can negatively affect the outcomes after an anterior cruciate ligament surgery.

An Autograft for Anterior Cruciate Ligament Reconstruction Results in Better Biomechanical Performance and Tendon-Bone Incorporation Than Does a Hybrid Graft in a Rat Model

BACKGROUND

The biomechanical and tendon-bone incorporation properties of allograft-augmented hybrid grafts for anterior cruciate ligament (ACL) reconstruction compared with traditional autografts are unknown.

HYPOTHESIS

Using an autograft for ACL reconstruction yields better results on biomechanical testing, radiographic analysis, and histological evaluation versus using a hybrid graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 66 adult male Sprague Dawley rats underwent unilateral ACL reconstruction with an autograft (AT group; n = 33) or a hybrid graft (HB group; n = 33). The grafts used in both groups were harvested from the peroneus longus tendon and were fixed by suturing to the surrounding periosteum. Samples were harvested for biomechanical testing, micro-computed tomography (CT), and histological evaluation at 4, 8, and 12 weeks postoperatively. Bone tunnels on the femoral and tibial sides were divided into 3 subregions: intra-articular (IA), midtunnel (MT), and extra-articular (EA). A cylinder-like volume of interest in the bone tunnel and a tubular-like volume of interest around the bone tunnel were used to evaluate new bone formation and bone remodeling, respectively, via micro-CT.

RESULTS

In the AT group, there were significantly higher failure loads and stiffness at 8 weeks (failure load: 3.04 ± 0.40 vs 2.09 ± 0.54 N, respectively; P = .006) (stiffness: 3.43 ± 0.56 vs 1.75 ± 0.52 N/mm, respectively; P < .001) and 12 weeks (failure load: 9.10 ± 1.13 vs 7.14 ± 0.94 N, respectively; P = .008) (stiffness: 4.45 ± 0.75 vs 3.36 ± 0.29 N/mm, respectively; P = .008) than in the HB group. With regard to new bone formation in the bone tunnel, in the AT group, the bone volume/total volume (BV/TV) was significantly higher than in the HB group on the tibial side at 8 weeks (IA: 22.21 ± 4.98 vs 5.16 ± 3.98, respectively; P < .001) (EA: 19.66 ± 7.19 vs 10.85 ± 2.16, respectively; P = .030) and 12 weeks (IA: 30.50 ± 5.04 vs 17.11 ± 7.31, respectively; P = .010) (MT: 21.15 ± 2.58 vs 15.55 ± 4.48, respectively; P = .041) (EA: 20.75 ± 3.87 vs 10.64 ± 3.94, respectively; P = .003). With regard to bone remodeling around the tunnel, the BV/TV was also significantly higher on the tibial side at 8 weeks (MT: 33.17 ± 8.05 vs 15.21 ± 7.60, respectively; P = .007) (EA: 25.19 ± 6.38 vs 13.94 ± 7.10, respectively; P = .030) and 12 weeks (IA: 69.46 ± 4.45 vs 47.80 ± 6.16, respectively; P < .001) (MT: 33.15 ± 3.88 vs 13.76 ± 4.07, respectively; P < .001) in the AT group than in the HB group. Sharpey-like fibers had formed at 8 weeks in the AT group. A large number of fibroblasts withdrew at 12 weeks. In the AT group, the width of the interface was significantly narrower at 4 weeks (85.86 ± 17.49 vs 182.97 ± 14.35 μm, respectively; P < .001), 8 weeks (58.86 ± 10.99 vs 90.15 ± 11.53 μm, respectively; P = .002), and 12 weeks (42.70 ± 7.96 vs 67.29 ± 6.55 μm, respectively; P = .001) than in the HB group.

CONCLUSION

Using an autograft for ACL reconstruction may result in improved biomechanical properties and tendon-bone incorporation compared with a hybrid graft.

CLINICAL RELEVANCE

Augmenting small autografts with allograft tissue may result in decreased biomechanical performance and worse tendon-bone incorporation, increasing the risk of graft failure.

Bioabsorbable interference screws can be used with less tunnel widening in anatomic rectangular tunnel anterior cruciate ligament reconstruction with a bone-patellar-tendon-bone graft

BACKGROUND

The purpose of this study was to investigate postoperative tunnel widening after rectangular tunnel bone-patellar-tendon-bone graft anterior cruciate ligament reconstruction using newer-generation bioabsorbable interference screws.

METHODS

Forty-six patients who had undergone primary rectangular tunnel bone-patellar-tendon-bone graft anterior cruciate ligament reconstruction using MILAGRO bioabsorbable interference screws (DePuy Synthes, Warsaw, IN, USA) for femoral fixation and for whom computed tomography was performed at two weeks and one year postoperatively were included in this prospective study. To assess the tunnel widening, the cross-sectional area of the femoral tunnel aperture (compared between two weeks and one year postoperatively) was assessed using computed tomography. Cyst formation, postoperative screw breakage, screw migration, and graft migration were also evaluated using computed tomography one year postoperatively.

RESULTS

Mean tunnel widening was 1.9%, and the cross-sectional area of the femoral tunnel aperture was not significantly different between two weeks and one year postoperatively. Postoperative cyst formation, screw breakage, screw migration, and graft migration were not observed in any patient.

CONCLUSIONS

After rectangular tunnel bone-patellar-tendon-bone graft anterior cruciate ligament reconstruction using bioabsorbable interference screws for femoral fixation, tunnel widening was not observed via computed tomography analysis at two weeks and one year postoperatively.

Independent Suture Tape Internal Brace Reinforcement of Bone-Patellar Tendon-Bone Allografts: Biomechanical Assessment in a Full-ACL Reconstruction Laboratory Model

Internal bracing for anterior cruciate ligament (ACL) surgery is a relatively new concept. The purpose of this study was to evaluate the effects of an "independent" button-fixed internal brace on the biomechanical properties of ACL reconstruction in a full-construct experimental model. Three groups (n = 10 each) were tested in a full-construct porcine-bone model with human bone-patellar tendon-bone allografts using different reconstruction techniques: interference screw fixation on femur and tibia (S-S group), adjustable-loop device (ALD) fixation on the femur with tibial interference screw without suture tape (ALD-S group), and with internal brace (ALD-S-IB group). Measured outcomes included cyclic displacement, stiffness, and ultimate load to failure. The ALD-S-IB group (2.9 ± 0.8 mm) displaced significantly less than the ALD-S (4.2 ± 0.9 mm; p = 0.015) and S-S group (4.3 ± 1.1 mm; p = 0.017). No significant difference was found between the ALD-S and the S-S group. Construct stiffness was significantly higher for the ALD-S-IB group (156 ± 23 N/mm) and the ALD-S group (122 ± 28 N/mm) than for the S-S group (104 ± 40 N/mm; p = 0.003 and p = 0.0042), but there was no significant difference between both ALD groups. Similarly, ultimate loads in the ALD-S-IB (758 ± 128 N) and the ALD-S groups (628 ± 223 N) were significantly greater than in the S-S group (416 ± 167 N; p < 0.001 and p = 0.025), but there was no significant difference between ALD groups. Adding an internal brace reinforcement to an ALD in a full-construct experimental model significantly decreased cyclic displacement by 31% without increasing construct stiffness or ultimate load significantly. These results indicate that suture tape internal bracing of bone-patellar tendon-bone allograft ACL reconstruction decreases cyclic displacement during experimental testing, which has clinical implications regarding initial construct stability.

Electrodeposition of calcium phosphate onto polyethylene terephthalate artificial ligament enhances graft-bone integration

It is a big challenge to develop a polyethylene terephthalate (PET) artificial ligament with excellent osteogenetic activity to enhance graft-bone integration for ligament reconstruction. Herein, we evaluated the effect of biomineralization (BM) and electrodeposition (ED) method for depositing calcium-phosphate (CaP) on the PET artificial ligament in vitro and in vivo. Scanning electron microscopy and energy-dispersive X-Ray spectrometer mapping analysis revealed that the ED-CaP had more uniform particles and element distribution (Ca, P and O), and thermogravimetric analysis showed there were more CaP on the PET/ED-CaP than the PET/BM-CaP scaffold. Moreover, the hydrophilicity of PET scaffolds was significantly improved after CaP deposition. In vitro study showed that CaP coating via BM or ED method could improve the attachment and proliferation of MC3T3-E1 cells, and ED-CaP coating significantly increased osteogenic differentiation of the cells, in which the Wnt/β-catenin signaling pathway might be involved. In addition, radiological, histological and immunohistochemical results of in vivo study in a rabbit anterior cruciate ligament (ACL) reconstruction model demonstrated that the PET/BM-CaP and PET/ED-CaP scaffolds significantly improved graft-bone integration process compared to the PET scaffold. More importantly, larger areas of new bone ingrowth and the formation of fibrocartilage tissue were observed at 12 weeks in the PET/ED-CaP group, and the biomechanical tests showed increased ultimate failure load and stiffness in PET/ED-CaP group compared to PET/BM-CaP and PET group. Therefore, ED of CaP is an effective strategy for the modification of PET artificial ligament and can enhance graft-bone integration both in vitro and in vivo.

BIOMECHANICAL EFFECTS OF DIFFERENT LENGTHS OF CROSS-PINS IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A FINITE ELEMENT ANALYSIS

Complication rates of anterior cruciate ligament reconstruction (ACL-R) were reported to be around 15%. Although it is a very common arthroscopic surgery with good outcomes, breakage and migration of fixators are still possible to occur due to stability issue. One of the factors that affects the mechanical stability of fixators is its length. Therefore, the aim of this paper is to analyze the biomechanical effects of different lengths of fixators (cross-pin technique) towards the stabilities of the knee joint after ACL-R. Finite element analyses of knee joint with DST grafts and fixators were carried out. Mimics and 3-Matic were used in the development of knee joint models, while the grafts and fixators were designed by using SolidWorks software. All models were remeshed in the 3-Matic and numerical analysis was performed via MSC.Marc Mentat software. A 100 N anterior tibial load was applied onto the tibia to simulate the anterior drawer test after the surgery and proximal femur was fixed at all degrees of freedom. Based on the findings, cross-pin with 40[Formula: see text]mm in length provided the most favorable option for better treatment of ACL-R, where it could promote osseointegration and preventing fracture.

Loop changes after knee flexion-extension movement in a cadaveric anterior cruciate reconstruction model

Background

Recently, adjustable-loop devices (ALDs) have been widely used, and their reliability has always been the focus of attention. This study compared loop length changes under pull stress caused by flexion and extension of the cadaver knee between ALDs and fixed-loop devices (FLDs) in terms of femoral fixation after anterior cruciate ligament (ACL) reconstruction.

Methods

ACL reconstruction in cadaveric knee joints was performed under arthroscopy with femoral suspension devices and tibial fixation by tying sutures on staples. The knee joint was repeatedly flexed and extended 30 times after fixation. According to the femoral fixation device used (Endobutton or Ultrabutton), the knee joints were divided into two groups: the ALD group (12 specimens) and the FLD group (ten specimens). The length of the loop before and after fixation was measured, and the loop length of the ALD group was re-measured 1 day after reconstruction.

Results

There was no significant difference in the length of the loop between the two groups (t = 0.579, P = 0.569). One day later, the loop length of the ALDs retracted by 0.29 ± 0.33 (0–1.1) mm, and there was no retraction in three specimens.

Conclusion

There was no significant difference in the loop length under flexion and extension stress after ACL reconstruction between ALDs and FLDs.

Effect of Nearly Isometric ACL Reconstruction on Graft-Tunnel Motion: A Quantitative Clinical Study

Background:

In anterior cruciate ligament (ACL) reconstruction, minimizing the graft-tunnel motion (GTM) will promote graft-to-bone healing and avoid graft loosening or tearing as well as potential bone tunnel enlargement. A nearly isometric state of the graft can be achieved by placing the tunnel properly to theoretically gain better graft-to-bone healing. However, little clinical evidence is available to quantify the relation between GTM and tunnel position.

Purpose:

To find the proper zones for the femoral and tibial tunnel apertures that minimize the GTM, referred to as the “nearly isometric zone,” through use of intraoperative GTM measurement and 3-dimensional computed tomography (3D-CT).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 100 patients were enrolled in this study. Nearly isometric ACL reconstruction was performed, and an intra-articular GTM measuring device was designed to measure and record the amplitude of GTM while the knee was flexed from 0° to 120°. Postoperatively, the patients underwent multislice CT, and the images were used to create 3D-CT models. After tibial aperture examination, 5 patients were excluded due to the divergence of tibial aperture, and therefore 95 patients remained in the study. Patients were divided into 2 groups according to whether the lateral intercondylar ridge was absent or present. The Bernard-Hertel grid coordinates (h, t) of the femoral tunnel were then quantified.

Results:

The maximal GTM (mGTM) was a mean ± SD of 1.06 ± 0.66 mm (range, 0.0-3.0 mm). The mGTM in patients with a lateral intercondylar ridge was significantly lower than that in patients without a lateral intercondylar ridge (0.81 ± 0.39 vs 1.59 ± 0.73 mm, respectively; P < .0001). The average h and t were 0.227 ± 0.079 and 0.429 ± 0.770, respectively. Notably, in 1 patient, the mGTM was 0 mm whereas the coordinates (h, t) of the femoral tunnel were 0.250 and 0.255. The overall GTM slowly increased before 90° but increased significantly after the knee was bent 105° (P = .010). Correlation analysis showed that the t coordiinate had significant correlation with mGTM (R = 0.581; P < .001). A gradient pattern was created to show the nearly isometric blue zone (mGTM <0.5 mm), which was found to overlap with the IDEAL (isometric, direct insertion, eccentric, anatomic, low tension-flexion pattern) position.

Conclusion:

A method of measuring intraoperative GTM and quantifying femoral tunnel position on postoperative 3D-CT was successfully developed. The presence of a lateral condylar ridge can significantly reduce mGTM. A nearly isometric zone was described that was consistent with the IDEAL concept.

Does Manual Drilling Improve the Healing of Bone-Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction? A Histological and Biomechanical Study in a Rabbit Model

Background:

Heat necrosis due to motorized drilling during anterior cruciate ligament (ACL) reconstruction could be a factor in delayed healing at the bone–tendon graft interface.

Hypothesis:

The process of osteointegration could be enhanced using manual drilling. It reduces the invasiveness of mechanical-thermal stress normally caused by the traditional motorized drill bit.

Study Design:

Controlled laboratory study.

Methods:

ACL reconstruction using semitendinosus tendon autografts was performed in 28 skeletally mature female New Zealand white rabbits, which were randomly divided into 3 groups. In group A (n = 12), the tunnels were drilled using a motorized device; in group B (n = 12), the tunnels were drilled using a manual drill bit; and group C (n = 4) served as a control with sham surgical procedures. The healing process in the tunnels was assessed histologically at 2, 4, 8, and 12 weeks and graded according to the Tendon–Bone Tunnel Healing (TBTH) scoring system. In addition, another 25 rabbits were used for biomechanical testing. The structural properties of the femur–ACL graft–tibia complex, from animals sacrificed at 8 weeks postoperatively, were determined using uniaxial tests. Stiffness (N/mm) and ultimate load to failure (N) were determined from the resulting load-elongation curves.

Results:

The time course investigation showed that manual drilling (group B) had a higher TBTH score and improved mechanical behavior, reflecting better organized collagen fiber continuity at the bone–fibrous tissue interface, better integration between the graft and bone, and early mineralized chondrocyte-like tissue formation at all the time points analyzed with a maximum difference at 4 weeks (TBTH score: 5.4 [group A] vs 12.3 [group B]; P < .001). Stiffness (23.1 ± 8.2 vs 17.8 ± 6.3 N/mm, respectively) and ultimate load to failure (91.8 ± 60.4 vs 55.0 ± 18.0 N, respectively) were significantly enhanced in the specimens treated with manual drilling compared with motorized drilling (P < .05 for both).

Conclusion:

The use of manual drilling during ACL reconstruction resulted in better tendon-to-bone healing during the crucial early weeks. Manual drilling was able to improve the biological and mechanical properties of bone–hamstring tendon graft healing and was able to restore postoperative graft function more quickly. Tunnel drilling results in bone loss and deficient tendon-bone healing, and heat necrosis after tunnel enlargement may cause mechanical stress, contributing to a delay in healing. Manual drilling preserved the bone stock inside the tunnel, reduced heat necrosis, and offered a better microenvironment for faster healing at the interface.

Clinical Relevance:

Based on study results, manual drilling could be used successfully in human ACL reconstruction, but further clinical studies are needed. A clinical alternative, called the original “all-inside” technique, has been developed for ACL reconstruction. In this technique, the femoral and tibial tunnels are manually drilled only halfway through the bone for graft fixation, reducing bone loss. Data from this study suggest that hamstring tendon–to–bone healing can be improved using a manual drilling technique to form femoral and tibial tunnels.

ACL reconstruction with adjustable-length loop cortical button fixation results in less tibial tunnel widening compared with interference screw fixation

PURPOSE

To compare tunnel widening and clinical outcome after anterior cruciate ligament reconstruction (ACLR) with interference screw fixation and all-inside reconstruction using button fixation.

METHODS

Tunnel widening was assessed using tunnel volume and diameter measurements on computed tomography (CT) scans after surgery and 6 months and 2 years later, and compared between the two groups. The clinical outcome was assessed after 2 years with instrumented tibial anteroposterior translation measurements, hop testing and International Knee Documentation Committee (IKDC), Lysholm and Tegner activity scores.

RESULTS

The study population at the final follow-up was 14 patients with screw fixation and 16 patients with button fixation. Tibial tunnels with screw fixation showed significantly larger increase in tunnel volume over time (P = 0.021) and larger tunnel diameters after 2 years in comparison with button fixation (P < 0.001). There were no significant differences in femoral tunnel volume changes over time or in tunnel diameters after 2 years. No significant differences were found in the clinical outcome scores.

CONCLUSIONS

All-inside ACLR using button fixation was associated with less tibial tunnel widening and smaller tunnels after 2 years in comparison with ACLR using screw fixation. The need for staged revision ACLRs may be greater with interference screws in comparison with button fixation at the tibial tunnel. The clinical outcomes in the two groups were comparable.

LEVEL OF EVIDENCE

II. RCT: Consort NCT01755819.