Effect of Calcium Phosphate-Hybridized Tendon Graft in Anatomic Single-Bundle ACL Reconstruction in Goats

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.

Safety and Osteointegration of Titanium Screws Coated with a Fibroblast Growth Factor-2-Calcium Phosphate Composite Layer in Non-Human Primates: A Pilot Study

Spinal instrumentation surgery for older patients with osteoporosis is increasing. Implant loosening may occur due to inappropriate fixation in osteoporotic bone. Developing implants that achieve stable surgical results, even in osteoporotic bone, can reduce re-operation, lower medical costs, and maintain the physical status of older patients. Fibroblast growth factor-2 (FGF-2) promotes bone formation; thus, coating pedicle screws with an FGF-2-calcium phosphate (FGF-CP) composite layer is hypothesized to enhance osteointegration in spinal implants. We designed a long-term implantation pilot study that estimated the safety and bone-forming efficacy of pedicle screws coated with an FGF-CP composite layer in cynomolgus monkeys. Titanium alloy screws, either uncoated (controls) or aseptically coated with an FGF-CP composite layer, were implanted in the vertebral bodies of six female adult cynomolgus monkeys (three monkeys per group) for 85 days. Physiological, histological, and radiographic investigations were performed. There were no serious adverse events, and no radiolucent areas were observed around the screws in either group. The bone apposition rate in the intraosseous region was significantly higher in the FGF-CP group than in the controls. Moreover, as analyzed by Weibull plots, the bone formation rate of the FGF-CP group exhibited a significantly higher regression line slope than the control group. These results demonstrated that there was significantly less risk of impaired osteointegration in the FGF-CP group. Our pilot study suggests that FGF-CP-coated implants could promote osteointegration, be safe, and reduce the probability of screw loosening.

Osteoinductive Bone Morphogenic Protein, Collagen Scaffold, Calcium Phosphate Cement, and Magnesium-Based Fixation Enhance Anterior Cruciate Ligament Tendon Graft to Bone Healing In Animal Models: A Systematic Review

PURPOSE

To perform a systematic literature review to analyze the results of the in vivo animal models and strategies that use osteoinductive materials to enhance the tendon graft-bone interface for anterior cruciate ligament reconstruction (ACLR).

METHODS

Following the Preferred Reporting Items for Systemic Reviews and Meta-Analysis guidelines, the PubMed, Embase, and Web of Science databases were searched. The inclusion criteria were studies of in vivo animal models of ACLR using a material to enhance tendon graft-bone interface healing and reporting at least the histologic results at the interface, along with radiologic and biomechanical data. Studies without control group or with another tendon-bone healing model were excluded. Methodologic quality was assessed with the Animal Research: Reporting In Vivo Experiments 1guidelines.

RESULTS

Twenty-seven studies met the inclusion criteria. Rabbit was the main animal model of ACLR, along with sheep and dog models. ACLR procedures varied widely between studies.. The main promising strategies and materials were wrapping the material around the graft, with a collagen scaffold loaded with an osteoinductive molecule (mostly bone morphogenetic proteins). The second strategy consisted of injecting the material at the tendon-bone interface; calcium phosphate cement or a derivative were the most used materials. Finally, using osteoinductive fixation devices was the third strategy; magnesium-based interference screws seemed to show most favorable results.

CONCLUSIONS

The studies retained had major methodologic flaws that limit the scope of these conclusions. However, based on histologic, biomechanical, and radiologic analyses, the most promising materials were a collagen scaffold loaded with an osteoinductive molecule and wrapped around the graft, calcium phosphate cement injected in the bone tunnel, and a magnesium-based fixation device.

CLINICAL RELEVANCE

In vivo animal models have identified several promising strategies and materials to optimize the tendon-bone interface after ACLR, but standardized and reproducible assessments are needed before these strategies can be adopted clinically.

Strategies for promoting tendon-bone healing: Current status and prospects

Tendon-bone insertion (TBI) injuries are common, primarily involving the rotator cuff (RC) and anterior cruciate ligament (ACL). At present, repair surgery and reconstructive surgery are the main treatments, and the main factor determining the curative effect of surgery is postoperative tendon-bone healing, which requires the stable combination of the transplanted tendon and the bone tunnel to ensure the stability of the joint. Fibrocartilage and bone formation are the main physiological processes in the bone marrow tract. Therefore, therapeutic measures conducive to these processes are likely to be applied clinically to promote tendon-bone healing. In recent years, biomaterials and compounds, stem cells, cell factors, platelet-rich plasma, exosomes, physical therapy, and other technologies have been widely used in the study of promoting tendon-bone healing. This review provides a comprehensive summary of strategies used to promote tendon-bone healing and analyses relevant preclinical and clinical studies. The potential application value of these strategies in promoting tendon-bone healing was also discussed.

Anterior Cruciate Ligament Reconstruction: Is Biological Augmentation Beneficial?

Surgical reconstruction in anterior cruciate ligament (ACL) ruptures has proven to be a highly effective technique that usually provides satisfactory results. However, despite the majority of patients recovering their function after this procedure, ACL reconstruction (ACLR) is still imperfect. To improve these results, various biological augmentation (BA) techniques have been employed mostly in animal models. They include: (1) growth factors (bone morphogenetic protein, epidermal growth factor, granulocyte colony-stimulating factor, basic fibroblast growth factor, transforming growth factor-β, hepatocyte growth factor, vascular endothelial growth factor, and platelet concentrates such as platelet-rich plasma, fibrin clot, and autologous conditioned serum), (2) mesenchymal stem cells, (3) autologous tissue, (4) various pharmaceuticals (matrix metalloproteinase-inhibitor alpha-2-macroglobulin bisphosphonates), (5) biophysical/environmental methods (hyperbaric oxygen, low-intensity pulsed ultrasound, extracorporeal shockwave therapy), (6) biomaterials (fixation methods, biological coatings, biosynthetic bone substitutes, osteoconductive materials), and (7) gene therapy. All of them have shown good results in experimental studies; however, the clinical studies on BA published so far are highly heterogeneous and have a low degree of evidence. The most widely used technique to date is platelet-rich plasma. My position is that orthopedic surgeons must be very cautious when considering using PRP or other BA methods in ACLR.

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.

[Application of transosseous suture in situ technique in repair of anterior cruciate ligament for multiple ligament injuries with knee dislocation]

Objective

To investigate the method and effectiveness of transosseous suture in situ technique in repairing anterior cruciate ligament (ACL) avulsion injury for the multiple ligament injuries with knee dislocation (MLIKD).

Methods

The clinical data of 27 patients (27 knees) with MLIKD between September 2010 and April 2016 were analyzed retrospectively. There were 21 males and 6 females, with an average age of 42 years (range, 24-60 years). The injury was caused by traffic accident in 9 cases, heavy-weight crushing in 9 cases, sports sprain in 6 cases, falling from height in 3 cases. The interval from injury to operation was 1-19 days (mean,10.8 days). There were 20 cases of femoral avulsion injury of ACL, 7 cases of tibial avulsion injury of ACL, and there were 17 cases of posterior cruciate ligament (PCL) injuries. According to the Schenck classification, there were 15 cases of KD-Ⅲ-M type, 8 cases of KD-Ⅲ-L type, and 4 cases of KD-Ⅳ type. All patients were positive in the posterior drawer test and Lachman test; 8 cases were degree Ⅲ positive in varus stress test, and 15 cases were degree Ⅲ positive in valgus stress test. The Lysholm score of knee was 27.6±6.5, the International Knee Documentation Committee (IKDC) score was 25.5±6.2, and the range of motion (ROM) of knee was (45.1±10.2)°. The injured PCL was reconstructed with a single bundle of autologous hamstring tendon. ACL was repaired with double bundle traction by transosseous suture in situ technique. Medial cruciate ligament, lateral cruciate ligament, joint capsule, and other damaged structures were repaired at the same time.

Results

All incisions healed by first intention. There were 3 cases with joint effusion and 3 cases with incomplete flexion. All patients were followed up 12-36 months (mean, 22 months). The X-ray films showed good stability in all directions. At last follow-up, the anterior and posterior drawer tests were all negative; Lachman test was degreeⅠpositive in 4 cases, valgus stress test was degreeⅠpositive in 3 cases, varus stress test was degreeⅠpositive in 1 case; and all tests were negative in the rest patients. At 1 year after operation, the ROM of knee was (119.3 ±12.6)°, Lysholm score was 87.2±6.3, and IKDC score was 87.9±6.3, showing significant differences when compared with the preoperative scores ( P<0.05).

Conclusion

Transosseous suture in situ technique can be used to repair the ACL avulsion injury for MLIKD, which can significantly improve the stability, mobility and function of the knee joint, and obtain satisfied short-term effectiveness.

Thermosensitive Chitosan-Gelatin-Glycerol Phosphate Hydrogels as Collagenase Carrier for Tendon-Bone Healing in a Rabbit Model

Healing of an anterior cruciate ligament graft in bone tunnel yields weaker fibrous scar tissue, which may prolong an already prolonged healing process within the tendon-bone interface. In this study, gelatin molecules were added to thermosensitive chitosan/β-glycerol phosphate disodium salt hydrogels to form chitosan/gelatin/β-glycerol phosphate (C/G/GP) hydrogels, which were applied to 0.1 mg/mL collagenase carrier in the tendon-bone junction. New Zealand white rabbit's long digital extensor tendon was detached and translated into a 2.5-mm diameter tibial plateau tunnel. Thirty-six rabbits underwent bilateral surgery and hydrogel injection treatment with and without collagenase. Histological analyses revealed early healing and more bone formation at the tendon-bone interface after collagenase partial digestion. The area of metachromasia significantly increased in both 4-week and 8-week groups after collagenase treatment (p < 0.01). Micro computed tomography showed a significant increase in total bone volume and bone volume/tissue volume in the 8 weeks after collagenase treatment, compared with the control group. Load-to-failure was significantly higher in the treated group at 8 weeks (23.8 ± 8.13 N vs 14.3 ± 3.9 N; p = 0.008). Treatment with collagenase digestion resulted in a 66% increase in pull-out strength. In conclusion, injection of C/G/GP hydrogel with collagenase improves tendon-to-bone healing in a rabbit model.

Safety and feasibility of using calcium phosphate hybridization method for quadriceps tendon-bone graft in anterior cruciate ligament reconstruction

Background

To improve tendon-to-bone healing in anterior cruciate ligament (ACL) reconstruction, a novel technique via the calcium phosphate (CaP) hybridization method for tendon graft using an alternate soaking process was developed. The use of the CaP hybridization method for quadriceps tendon-bone (QTB) graft in ACL reconstruction has not been reported in previous studies. Thus, this clinical trial aimed to clarify the safety and feasibility of using CaP hybridization method for quadriceps tendon-bone (QTB) graft in ACL reconstruction.

Methods

Eight patients (average age, 41.6 ± 10.6 years; 2 men and 6 women) with unilateral ACL injury were included in this study. They underwent ACL reconstruction using QTB graft that hybridized CaP. The follow-up period was from 2 months to 4 years (average, 2.4 ± 1.5 years). Cases of adverse events, including tumor formation, infection, fracture, contracture, severe pain, and re-rupture, were recorded. Moreover, clinical results (KT-1000 arthrometry, pivot-shift test, International Knee Documentation Committee grade, Lysholm scale, and sports activity level), and images of graft and bone tunnel (magnetic resonance imaging, arthroscopic appearance, and computed tomography) were also evaluated.

Results

No adverse events were observed in the follow-up periods. Postoperative clinical results showed improvement compared with the preoperative findings. The sports activity level after the surgery became equivalent to that before injury. There was no progression of bone tunnel enlargement.

Conclusions

Using the CaP hybridization method for QTB graft in ACL reconstruction was safe and feasible in the clinical trial. Moreover, this method may improve clinical outcomes. In the future, it is necessary to verify the effect of the CaP hybridization method for QTB graft in ACL reconstruction.

Morphological changes in the femoral and tibial bone tunnels after anatomic single-bundle anterior cruciate ligament reconstruction using a calcium phosphate-hybridized tendon graft in 2years of follow-up

INTRODUCTION

A calcium phosphate (CaP)-hybridized tendon graft improves tendon-to-bone healing. The purpose of the study was to evaluate the progression of morphological changes in the femoral and tibial bone tunnels after anatomic single-bundle anterior cruciate ligament (ACL) reconstruction using the CaP-hybridized tendon graft versus an untreated tendon graft during 2 years of follow-up.

HYPOTHESIS

We hypothesized that the CaP-hybridized tendon graft would prevent the progression of bone tunnel enlargement compared with the untreated tendon graft.

PATIENTS AND METHODS

The CaP group comprised 19 patients, while the conventional group comprised 18. Computed tomography was performed at postoperative 1 week, 1 year, and 2 years. The bone tunnel enlargement and tunnel translation at the aperture of the femoral and tibial tunnels were analyzed.

RESULTS

In the CaP group, the femoral bone tunnel did not expand during 2 years of follow-up. In the conventional group, the femoral bone tunnel diameters at postoperative 1 year and 2 years were enlarged compared with postoperative 1 week, and the proximal and distal walls of the femoral bone tunnel shifted proximally and distally, respectively. The femoral bone tunnel in the CaP group was smaller than that in the conventional group at 1 year postoperatively. Although the tibial bone tunnels expanded for up to 1 year postoperatively in both groups, the expanded bone tunnel reduced during 2 years of follow-up only in the CaP group.

DISCUSSION

In anatomic single-bundle ACL reconstruction, the femoral bone tunnel in the CaP group did not expand or progress with time compared with the conventional group, while the tibial bone tunnel in the CaP group expanded for up to 1 year postoperatively and then reduced for up to 2 years postoperatively. The CaP-hybridized tendon can prevent the progression of bone tunnel enlargement.

LEVEL OF EVIDENCE

Level II, Low-powered prospective randomized trial.

Anatomic single-bundle anterior cruciate ligament reconstruction using a calcium phosphate-hybridized tendon graft: a randomized controlled trial with 2 years of follow-up

BACKGROUND

To improve tendon-to-bone healing in anterior cruciate ligament (ACL) reconstruction, a novel technique via calcium phosphate (CaP)-hybridized tendon graft using an alternate soaking process was developed. The purpose of this study was to evaluate the clinical results of anatomic single-bundle ACL reconstruction using the CaP-hybridized tendon graft with up to 2 years follow-up, and compare the outcome with conventional ACL reconstruction and preoperative data.

METHODS

Ninety patients who required anatomic single-bundle ACL reconstruction were randomized to undergo either the CaP-hybridized tendon graft method (CaP group, n = 45) or the conventional method (conventional group, n = 45). At 1 and 2 years postoperatively, all patients were evaluated using KT-1000 arthrometry, pivot-shift test, International Knee Documentation Committee (IKDC) grade, Lysholm scale, and Tegner scale; at the same timepoints, bone tunnel enlargement was evaluated using computed tomography, and the tendon graft intensity was evaluated on magnetic resonance imaging. Tendon graft appearance was evaluated arthroscopically once after a period of up to 2 years postoperatively. Cases of re-rupture and adverse events were recorded in both groups.

RESULTS

In both groups, the KT-1000 arthrometry, pivot-shift test, IKDC grade, and Lysholm scale results at 1 and 2 years postoperatively were superior to preoperative data; these results did not significantly differ between groups at either timepoint. The rate of increase of the cross-sectional area of the femoral bone tunnel in the CaP group was smaller than that in the conventional group at 1 year postoperatively. The other results did not significantly differ between the two groups at any timepoint. There were two cases of re-rupture in the CaP group, and six cases of re-rupture in the conventional group. There were no adverse events during follow-up in either group.

CONCLUSIONS

Anatomic single-bundle ACL reconstruction using a CaP-hybridized tendon graft was safe, and resulted in improved clinical outcomes at 2 years postoperatively compared with preoperative data; the outcomes were comparable with the conventional method. A longer follow-up is needed to clarify the clinical effects of the CaP-hybridized tendon graft in anatomic single-bundle ACL reconstruction.

TRIAL REGISTRATION

UMIN, UMIN000019788 Registered 14 November 2015-Retrospectively registered.

Biological augmentation of graft healing in anterior cruciate ligament reconstruction: a systematic review

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

Materials and Methods

In all, 1879 studies were identified across three databases. Following assessment against strict criteria, 112 studies were included (20 clinical studies; 92 animal studies).

Results

Seven categories of biological interventions were identified: growth factors, biomaterials, stem cells, gene therapy, autologous tissue, biophysical/environmental, and pharmaceuticals. The methodological quality of animal studies was moderate in 97%, but only 10% used clinically relevant outcome measures. The most interventions in clinical trials target the graft-tunnel interface and are applied intraoperatively. Platelet-rich plasma is the most studied intervention, but the clinical outcomes are mixed, and the methodological quality of studies was suboptimal. Other biological therapies investigated in clinical trials include: remnant-augmented ACLR; bone substitutes; calcium phosphate-hybridized grafts; extracorporeal shockwave therapy; and adult autologus non-cultivated stem cells.

Conclusion

There is extensive preclinical research supporting the use of biological therapies to augment ACLR. Further clinical studies that meet the minimum standards of reporting are required to determine whether emerging biological strategies will provide tangible benefits in patients undergoing ACLR. Cite this article: Bone Joint J 2018;100-B:271-84.

Co-injection of human adipose stromal cells and rhBMP-2/fibrin gel enhances tendon graft osteointegration in a rabbit anterior cruciate ligament-reconstruction model

The objective of this study was to investigate whether the co-injection of human adipose stromal cells (hASCs) and rhBMP-2/fibrin gel into the bone tunnels of anterior cruciate-ligament reconstructions can effectively enhance tendon graft osteointegration. We performed bilateral reconstructions using autologous semitendinosus tendons in 45 New Zealand rabbits, which we divided into three groups. We injected the bone tunnels with fibrin gel for group 1, rhBMP-2 (1 μg/ml)/fibrin gel for group 2, and hASCs wrapped in rhBMP-2 (1 μg/ml)/fibrin gel for group 3. We sacrificed five rabbits (two for histological assessment and three for biomechanical tests) from each group at 2, 4, and 8 weeks post surgery. At 2 and 4 weeks post surgery, histological analysis showed that fibro-cartilage had appeared in the tendon-bone interface in group 2. At 4 weeks post surgery, mature bone cells could be seen in group 3. There was new bone formed between the host bone and the graft in groups 2 and 3 at 8 weeks post surgery. Biomechanical testing showed that at 4 and 8 weeks post surgery, the ultimate failure loads in group 3 were significantly higher than those in groups 1 and 2 (both P=0.01). The tendon stiffness in group 3 was significantly higher than that in the other groups at 4 weeks post surgery (P=0.01). Our results indicate that co-injection of hASCs and rhBMP-2/fibrin gel has the potential to promote tendon-bone healing after anterior cruciate-ligament reconstruction.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

I.

Differences in placement of calcium phosphate-hybridized tendon grafts within the femoral bone tunnel during ACL reconstruction do not influence tendon-to-bone healing

Background

Calcium phosphate (CaP)-hybridization of tendon grafts has been shown to improve tendon-to-bone healing. The purpose of this study was to clarify the influence of different tendon graft placement methods on tendon-to-bone healing using CaP-hybridized tendon grafts in anterior cruciate ligament (ACL) reconstructions in rabbits.

Methods

We compared two methods of tendon graft placement within the femoral bone tunnel: suspension of the tendon graft within the bone tunnel (suspension group) and implantation of the tendon graft coherent with the bone socket (coherence group). CaP-hybridized tendon grafts were used in both groups. Fifty-six male Japanese white rabbits were used for this study. The results of biomechanical tests (n = 9) and histological analyses (n = 5) were evaluated at 2 and 4 weeks after surgery.

Results

The ultimate failure load, stiffness, stress, soft tissue remaining in bone tunnel after biomechanical testing, and direct bonding area at tendon–bone interface did not differ significantly between the suspension and coherence groups at either 2 or 4 weeks after surgery (p > 0.05). In both groups, the ultimate failure load, stress, soft tissue remaining in the bone tunnel, and direct bonding area at interface at 4 weeks after surgery were significantly greater than those at 2 weeks after surgery (p < 0.05).

Conclusions

Tendon-to-bone healing in both groups progressed until the endpoint of 4 weeks. There was no influence of the CaP-hybridized tendon graft placement method on tendon-to-bone healing at 4 weeks after ACL reconstruction in rabbits. Thus, the CaP-hybridized tendon grafts were unaffected by differences in their placement within the bone tunnel and became equally anchored to the bone tunnel during the early postoperative period. The tendon graft placement method may not influence tendon-to-bone healing in ACL reconstruction when CaP-hybridized tendon grafts are used.

Comparison of postoperative biomechanical function between anatomic double-bundle and single-bundle ACL reconstructions using calcium phosphate-hybridized tendon grafts in goats

BACKGROUND

Calcium phosphate (CaP)-hybridized tendon grafts improved biomechanical function compared with untreated grafts after single-bundle (SB) anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the biomechanical function between anatomic double-bundle (DB) and single-bundle (SB) ACL reconstructions using CaP-hybridized tendon grafts at 6 months postoperatively in goats.

HYPOTHESIS

We hypothesized that the postoperative biomechanical function in the DB group will be better than that in the SB group.

MATERIALS AND METHODS

Knee kinematics and in situ forces in the grafts under applied anterior tibial load (ATL) of 50N and internal tibial torque (ITT) of 2.0 Nm at full extension, and 60° and 90° of knee flexion, and the histology of the tendon-bone interface were compared between the DB group (n=6) and SB group (n=6).

RESULTS

The in situ forces under ATL in the DB group at full extension and 90°of knee flexion were greater than those in the SB group. The in situ forces under ITT in the DB group at full extension and 60°of knee flexion were greater than those in the SB group. The in situ forces on the posterolateral bundle of the grafts under ATL and ITT in the DB group at full knee extension were greater than those on the posterior half of the grafts in the SB group. The histology did not differ significantly between the groups.

CONCLUSIONS

Although CaP-hybridized tendon grafts were used in both groups, the in situ forces under ATL and ITT in the DB group were greater than those in the SB group at 6 months postoperatively. The posterolateral bundle of the grafts in the DB group acted effectively against both ATL and ITT at full extension. The tendon-to-bone healing was similar in both groups.

STUDY DESIGN

Controlled laboratory study. Level 2.