Histologic and biomechanical analysis of anterior cruciate ligament graft to bone healing in skeletally immature sheep

Assessment of the advantages and limitations of an innovative silk fibroin scaffold for the reconstruction of the anterior cruciate ligament with preclinical in vitro and in vivo evaluations

The gold standard treatment in anterior cruciate ligament (ACL) reconstruction involves autologous tissue transplantation, but this can have complications. Artificial grafts are an alternative, but the best option is debated. This study aimed to assess the biocompatibility and integration of a silk fibroin textile prosthesis (SF-TP) with peri-implant bone tissue and the native ACL. Twenty-six sheep underwent ACL reconstruction with SF-TP or autologous femoral fascia lata (FFL). Sheep were divided into two groups (3 and 6 months) and retrieved joints processed for histological, morphometrical and mechanical analysis. In vitro, SF-TP showed no cytotoxicity and good cell interaction up to 14 days. Histology revealed fibro-vascular tissue around SF-TP, with a progressive attempt of ligamentous-like tissue formation at 6 months. However, SF-TP group had higher joint damage scores. Micro-CT showed tunnel enlargement in SF-TP group, while FFL group had a decrease. SF-TP reconstructions had lower stiffness and strength (44 % and 64 % decrease) than those of autologous FFL reconstruction and often failed by pull-out from the bone tunnel due to tunnel enlargement. These results indicate poor osteointegration and graft motion with SF-TP, leading to joint damage/bone resorption and reduced mechanical competence. These results do not support the use of SF-TP for ACL reconstruction.

Transphyseal arthroscopic anterior cruciate ligament reconstruction in children under 12 years

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries in children is on the rise. Despite this trend, the optimal management of these injuries remains a matter of ongoing debate. In this light, our study seeks to assess the clinical, radiological, and functional outcomes of transphyseal ACL reconstruction in preadolescent patients in the medium-term.

METHODS

This prospective study included preadolescent patients aged up to 12 years who underwent ACL transphyseal reconstruction between 2010 and 2020 and had a minimum follow-up of 2 years. Clinical assessments encompassed joint stability and range of motion. Furthermore, leg length discrepancy (LLD) and femorotibial alignment were evaluated both clinically and radiologically using full-length lower limb standing radiographs. Pre- and postoperative functional outcomes were assessed using the International Knee Documentation Committee (IKDC) and Lysholm scales, and the return to normal sports activity was evaluated using the ACL-Return to Sport after Injury (ACL-RSI) scale. Complications and relevant follow-up data were also recorded. Statistical analyses were conducted to evaluate these outcomes.

RESULTS

A total of 35 preadolescent patients, consisting of 24 males and 11 females, with a mean age at surgery of 11.2 ± 0.7 years (8.7-12), were included in the study. The mean follow-up was 52.3 ± 20.7 months (24.1-95.9). No significant growth disturbances or clinically relevant LLD were evidenced. All patients demonstrated clinically stable knees with full range of motion at the 2-year follow-up. There were statistically significant improvements in pre- and postoperative IKDC (39.3 ± 13.5 vs. 99.7 ± 0.8, p < 0.005) and Lysholm scores (48.2 ± 15.1 vs. 99.6 ± 1.4, p < 0.005). All but two patients were able to return to their pre-injury level of sports activity, with a mean ACL-RSI score of 93.5 ± 1.3. The analysis revealed an 8.6% rerupture rate and an 11.4% rate of contralateral ACL injuries, with 5-year survival rates of 92.3% and 88.8%, respectively. Subgroup analyses based on age, gender, surgical delay, or associated meniscal lesions did not reveal any significant differences in functional outcomes. Additionally, there was no discernible relationship between age or timing of ACL reconstruction and the risk of meniscal injuries.

CONCLUSIONS

Our study reinforces the value of ACL reconstruction in skeletally immature preadolescent patients, with transphyseal technique proven to be a safe, effective, and technically simpler option, even for children under the age of 12. The findings indicate excellent functional outcomes, a high rate of successful return to sporting activities, and minimal to no incidence of growth-related complications in the medium-term.

LEVEL OF EVIDENCE

Level II, prospective comparative cohort study, before and after intervention.

Mechanical properties of animal ligaments: a review and comparative study for the identification of the most suitable human ligament surrogates

The interest in the properties of animal soft tissues is often related to the desire to find an animal model to replace human counterparts due to the unsteady availability of human tissues for experimental purposes. Once the most appropriate animal model is identified, it is possible to carry out ex-vivo and in-vivo studies for the repair of ligamentous tissues and performance testing of replacement and support healing devices. This work aims to present a systematic review of the mechanical properties of ligaments reported in the scientific literature by considering different anatomical regions in humans and several animal species. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. Moreover, considering the lack of a standard protocol for preconditioning of tissues, this aspect is also addressed. Ninety-six studies were selected for the systematic review and analysed. The mechanical properties of different animal species are reported and summarised in tables. Only results from studies reporting the strain rate parameter were considered for comparison with human ligaments, as they were deemed more reliable. Elastic modulus, ultimate tensile stress, and ultimate strain properties are graphically reported identifying the range of values for each animal species and to facilitate comparison between values reported in the scientific literature in animal and human ligaments. Useful similarities between the mechanical properties of swine, cow, and rat and human ligaments have been found.

Imaging Findings of Complications After Lateral Extra-Articular Tenodesis of the Knee: A Current Concepts Review

Background

Despite successful anterior cruciate ligament (ACL) reconstruction, many patients continue to experience persistent anterolateral rotatory instability. Lateral extra-articular tenodesis (LET) is used to address this instability by harvesting a portion of the iliotibial band, passing it underneath the fibular collateral ligament, and attaching it just proximal and posterior to the lateral femoral epicondyle. Based on the most recent clinical evidence, the addition of LET to ACL reconstruction improves clinical outcomes, which has led to an increase in the use of this technique.

Purpose

To provide an overview of the postoperative complications of the LET procedure and their associated imaging findings, with a focus on magnetic resonance imaging (MRI).

Study Design

Narrative review.

Methods

In this scoping review, the authors reviewed available radiographic, computed tomography, and MRI scans of patients who experienced postoperative complications after ACL reconstruction with LET, in which the complication was determined to be from the LET procedure. Images were reviewed and subsequently described by an on-staff musculoskeletal radiologist.

Results

The authors found 9 different complications associated with LET: graft failure, hematoma, infection, chronic pain, tunnel convergence, fixation device migration, muscular hernia, peroneal nerve palsy, and knee stiffness. They supplemented these findings with radiographic evidence from 6 patients.

Conclusion

As extra-articular reconstruction techniques including LET become more popular among orthopaedic surgeons, it is important that radiologists and surgeons be adept at recognizing the normal imaging findings of LET and associated complications.

Time-series biological responses toward decellularized bovine tendon graft and autograft for 52 consecutive weeks after rat anterior cruciate ligament reconstruction

There is an essential demand for developing biocompatible grafts for knee anterior cruciate ligament reconstruction (ACLR). This study investigated cell infiltration into decellularized bovine tendon xenografts using a rat knee ACLR model. Twelve-week-old Sprague–Dawley rats were used. At weeks 1, 2, 4, 8, 16, 26, and 52 (each period, n = 6) after ACLR, rats receiving decellularized bovine tendon (group D, n = 42) or autologous tendon (group A, n = 42) as grafts underwent peritibial bone tunnel bone mineral density (BMD), histological, and immunohistological assessments. BMD increased over time in both the groups until week 16 and then remained unchanged without exhibiting significant differences between the groups. Initially, cellularity in group D was lower than that in group A; however, by weeks 4–8, both the groups were comparable to the native anterior cruciate ligament group and cellularity remained unchanged until week 52. Initially, group A had more M1 macrophages, indicating inflammation, whereas group D had more M2 macrophages, indicating tissue regeneration. Nonetheless, the M1 and M2 macrophage counts of both the groups were comparable at most times. This study revealed the excellent recellularization and tendon–bone integration abilities of decellularized tendons using a cross-species model.

Integration and functional performance of a decellularised porcine superflexor tendon graft in an ovine model of anterior cruciate ligament reconstruction

The objective was to evaluate the performance of decellularised porcine superflexor tendon (pSFT) as an anterior cruciate ligament (ACL) reconstruction device. The ACL of adult sheep was reconstructed with decellularised pSFT or ovine allograft SFT and animals sacrificed at 4, 12 and 26 weeks (n = 4 per group) for biological evaluation and 26 weeks (n = 6) for biomechanical evaluation of the grafts. Both grafts showed good in vivo performance with no major differences at macroscopic evaluation post euthanasia. Histopathology revealed an inflammatory reaction to both grafts at 4 weeks, which reduced by 26 weeks. There was advanced cellular ingrowth from 12 weeks, ligamentisation of intra-articular grafts, ossification and formation of Sharpey's fibers at the graft/bone junctions. Immunohistochemistry showed that at 4 and 12 weeks, the host response was dominated by CD163+ M2 macrophages and a cell infiltrate comprising α-SMA + myofibroblasts, CD34+ and CD271+ progenitor cells. At 26 weeks the biomechanical properties of decellularised pSFT and oSFT grafts were comparable, with all grafts failing in the intra-articular region. This study provides new insight into constructive remodelling of tendons used for ACL replacement and evidence of integration and functional performance of a decellularised xenogeneic tendon with potential as an alternative for ACL reconstruction.

Change in Collagen Fibril Diameter Distribution of Bovine Anterior Cruciate Ligament upon Injury Can Be Mimicked in a Nanostructured Scaffold

More than 200,000 people are suffering from Anterior Cruciate Ligament (ACL) related injuries each year in the US. There is an unmet clinical demand for improving biological attachment between grafts and the host tissue in addition to providing mechanical support. For biological graft integration, it is important to provide a physiologically feasible environment for the host cells to enable them to perform their duties. However, behavior of cells during ACL healing and the mechanism of ACL healing is not fully understood partly due to the absence of appropriate environment to test cell behavior both in vitro and in vivo. This study aims at (i) investigating the change in fibril diameter of bovine ACL tissue upon injury and (ii) fabricating nanofiber-based scaffolds to represent the morphology and structure of healthy and injured ACL tissues. We hypothesized that distribution and mean diameter of ACL fibrils will be altered upon injury. Findings revealed that the collagen fibril diameter distribution of bovine ACL changed from bimodal to unimodal upon injury with subsequent decrease in mean diameter. Polycaprolactone (PCL) scaffold fiber diameter distribution exhibited similar bimodal and unimodal distribution behavior to qualitatively represent the cases of healthy and injured ACL, respectively. The native ACL tissue demonstrated comparable modulus values only with the aligned bimodal PCL scaffolds. There was significant difference between mechanical properties of aligned bimodal and unaligned unimodal PCL scaffolds. We believe that the results obtained from measurements of diameter of collagen fibrils of native bovine ACL tissue can serve as a benchmark for scaffold design.

Postoperative radiographic observations following transphyseal anterior cruciate ligament reconstruction in skeletally immature patients

OBJECTIVE

To characterize the changes to bone tunnels, graft fixation devices, and physes that occur on radiographs of skeletally immature individuals at least 2 years after transphyseal anterior cruciate ligament reconstruction (ACLR).

MATERIALS AND METHODS

Skeletally immature patients who underwent transphyseal ACLR were recruited to complete postoperative assessment at ≥ 2 years. The dimensions of tibial and femoral bone tunnels, position of graft fixation devices, and presence of growth arrest were assessed on radiographs, and pain visual analog and International Knee Documentation Committee scores were obtained. Paired t tests were used for comparisons.

RESULTS

Nine patients were included with an average follow-up of 4.6 years postoperatively. There were no cases of premature physeal closure postoperatively and clinical outcome measures were excellent in all patients. The length of the intra-articular portion of anterior cruciate ligament graft increased postoperatively (P = 0.01). Distance between the tibial hardware and proximal tibial physis also increased over time on anteroposterior (P = 0.001) and lateral (P = 0.003) radiographs. However, the distance between the femoral hardware and distal femoral physis was unchanged and in five patients was associated with proximal femoral tunnel enlargement.

CONCLUSION

Proximal femoral tunnel expansion and lack of proximal migration of the femoral button were seen in more than half of our patients. However, these findings had no detrimental effects on clinical outcome measures or remaining skeletal growth.

2018 International Olympic Committee Consensus Statement on Prevention, Diagnosis, and Management of Pediatric Anterior Cruciate Ligament Injuries

In October 2017, the International Olympic Committee hosted an international expert group of physical therapists and orthopaedic surgeons who specialize in treating and researching pediatric anterior cruciate ligament (ACL) injuries. The purpose of this meeting was to provide a comprehensive, evidence-informed summary to support the clinician and help children with ACL injury and their parents/guardians make the best possible decisions. Representatives from the following societies attended: American Orthopaedic Society for Sports Medicine; European Paediatric Orthopaedic Society; European Society for Sports Traumatology, Knee Surgery, and Arthroscopy; International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine; Pediatric Orthopaedic Society of North America; and Sociedad Latinoamericana de Artroscopia, Rodilla, y Deporte. Physical therapists and orthopaedic surgeons with clinical and research experience in the field and an ethics expert with substantial experience in the area of sports injuries also participated. This consensus statement addresses 6 fundamental clinical questions regarding the prevention, diagnosis, and management of pediatric ACL injuries. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision making with children and the potential long-term ramifications of the injury.

2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries

In October 2017, the International Olympic Committee hosted an international expert group of physiotherapists and orthopaedic surgeons who specialise in treating and researching paediatric ACL injuries. Representatives from the American Orthopaedic Society for Sports Medicine, European Paediatric Orthopaedic Society, European Society for Sports Traumatology, Knee Surgery & Arthroscopy, International Society of Arthroscopy Knee Surgery and Orthopaedic Sports Medicine, Pediatric Orthopaedic Society of North America and Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte attended. Physiotherapists and orthopaedic surgeons with clinical and research experience in the field, and an ethics expert with substantial experience in the area of sports injuries also participated. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision-making with children and the potential long-term ramifications of the injury. This consensus statement addresses six fundamental clinical questions regarding the prevention, diagnosis and management of paediatric ACL injuries. The aim of this consensus statement is to provide a comprehensive, evidence-informed summary to support the clinician, and help children with ACL injury and their parents/guardians make the best possible decisions.

2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries

In October 2017, the International Olympic Committee hosted an international expert group of physiotherapists and orthopaedic surgeons who specialise in treating and researching paediatric anterior cruciate ligament (ACL) injuries. Representatives from the American Orthopaedic Society for Sports Medicine, European Paediatric Orthopaedic Society, European Society for Sports Traumatology, Knee Surgery and Arthroscopy, International Society of Arthroscopy Knee Surgery and Orthopaedic Sports Medicine, Pediatric Orthopaedic Society of North America, and Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte attended. Physiotherapists and orthopaedic surgeons with clinical and research experience in the field, and an ethics expert with substantial experience in the area of sports injuries also participated. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision-making with children and the potential long-term ramifications of the injury. This consensus statement addresses six fundamental clinical questions regarding the prevention, diagnosis, and management of paediatric ACL injuries. The aim of this consensus statement is to provide a comprehensive, evidence-informed summary to support the clinician, and help children with ACL injury and their parents/guardians make the best possible decisions.

Digital image correlation-aided mechanical characterization of the anteromedial and posterolateral bundles of the anterior cruciate ligament

The anterior cruciate ligament (ACL) is one of the most commonly injured soft tissue structures in the articular knee joint, often requiring invasive surgery for patients to restore pre-injury knee kinematics. There is a pressing need to understand the role of the ACL in knee function, in order to select proper replacements. Digital image correlation (DIC), a non-contact full field displacement measurement technique, is an established tool for evaluating non-biological materials. The application of DIC to soft tissues has been in the nascent stages, largely due to patterning challenges of such materials. The ACL is notoriously difficult to mechanically characterize, due to the complex geometry of its two bundles and their insertions. This paper examines the use of DIC to determine the tensile mechanical properties of the AM and PL bundles of ovine ACLs in a well-known loading state. Homogenous loading in the mid-substance of the bundles provides for accurate development of stress/strain curves using DIC. Animal to animal variability is reduced, and the bundles are stiffer than previously thought when tissue-level strains are accurately measured.

STATEMENT OF SIGNIFICANCE

The anterior cruciate ligament (ACL), a major stabilizing ligament of the articular knee joint, is one of the most commonly injured soft tissue structures in the knee. Often, invasive surgery is required to restore pre-injury knee kinematics, and there are several long-term consequences of ACL reconstructions, including early-onset osteoarthritis. The role of the ACL in knee stability and motion has received much attention in the biomechanics community. This paper examines the use of a non-contact full-field displacement measurement technique, digital image correlation, to determine the tensile mechanical properties of the ACL. The focus of this work is to investigate the intrinsic mechanical properties of the ACL, as new knowledge in these areas will aid clinicians in selecting ACL replacements.

Incorporation of Hamstring Grafts Within the Tibial Tunnel After Anterior Cruciate Ligament Reconstruction: Magnetic Resonance Imaging of Suspensory Fixation Versus Interference Screws

BACKGROUND

The success of anterior cruciate ligament (ACL) reconstruction requires solid graft incorporation within the tunnels to enable graft remodeling. Resorbable interference screws (RIS) provide limited tendon-bone contact because much of the tunnel circumference is occupied by the screw itself, while adjustable suspensory fixation (ASF) systems provide larger contact zones, which favor ligamentization.

PURPOSE

To evaluate ligamentization of a 4-strand semitendinosus (4ST) graft fixed with ASF compared with RIS within the tibial bone tunnel at 6 months postoperatively using magnetic resonance imaging (MRI).

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

We prospectively enrolled 121 consecutive patients undergoing primary ACL reconstruction using a single-bundle 4ST graft. The femoral end of the graft was fixed using suspensory fixation in all knees. The tibial end of the graft was fixed using ASF in 67 knees and RIS in 54 knees. Six months postoperatively, knee laxity measurements were taken, and MRI was performed to assess graft incorporation within the tibial tunnel.

RESULTS

At 6-month follow-up, MRI scans of 109 knees were available for analysis. The mean tibial tunnel enlargement in the ASF group was 2.3 ± 1.1 mm (range, 0.5-6.0 mm), while in the RIS group, it was 4.7 ± 2.8 mm (range, 0.5-19.0 mm) (P < .001). The Howell graft signal assessment findings were excellent in 97% of knees in the ASF group and in 25% of knees in the RIS group (P < .001). The mean signal-to-noise quotient (SNQ) was 0.078 ± 0.62 in the ASF group and 0.671 ± 0.83 in the RIS group (P < .001).

CONCLUSION

ASF provides more favorable conditions than RIS for the incorporation and ligamentization of 4ST grafts within the tibial tunnel. The ASF system used showed very little tunnel widening, which suggests that it grants stabilization. The SNQ was also considerably better in the ASF group.

Large animal models in experimental knee sports surgery: focus on clinical translation

Large animal models play a crucial role in sports surgery of the knee, as they are critical for the exploration of new experimental strategies and the clinical translation of novel techniques. The purpose of this contribution is to provide critical aspects of relevant animal models in this field, with a focus on paediatric anterior cruciate ligament (ACL) reconstruction, high tibial osteotomy, and articular cartilage repair. Although there is no single large animal model strictly replicating the human knee joint, the sheep stifle joint shares strong similarities. Studies in large animal models of paediatric ACL reconstruction identified specific risk factors associated with the different surgical techniques. The sheep model of high tibial osteotomy is a powerful new tool to advance the understanding of the effect of axial alignment on the lower extremity on specific issues of the knee joint. Large animal models of both focal chondral and osteochondral defects and of osteoarthritis have brought new findings about the mechanisms of cartilage repair and treatment options. The clinical application of a magnetic device for targeted cell delivery serves as a suitable example of how data from such animal models are directly translated into in clinical cartilage repair. As novel insights from studies in these translational models will advance the basic science, close cooperation in this important field of clinical translation will improve current reconstructive surgical options and open novel avenues for regenerative therapies of musculoskeletal disorders.

Surgical-experimental principles of anterior cruciate ligament (ACL) reconstruction with open growth plates

Objective

To review surgical and animal experimental studies performed with open growth plates in relation with pediatric anterior cruciate ligament (ACL) reconstruction.

Backround

When it comes to the treatment of ACL injured children, there is a lack of current international guidelines, leaving the treating physicians with a therapeutic dilemma. A variety of surgical and animal experimental studies have been undertaken over the last decades in relation with open growth plates and ACL-reconstruction.

Method

Based on our own previous animal experimental data, we highlighted 15 specific points concerning pediatric ACL-reconstruction and reviewed additional literature concerning these individual items.

Results

Pediatric ACL-reconstruction could be proven to be safe in animal models. Growth abnormalities, risk factors and factors, which were specifically related to biological healing processes in children, were identified. From them surgical principles for safe pediatric ACL replacements can be deducted. Applying these principles through a correct technical execution of surgery may prevent clinically significant growth changes.

Conclusion

Over the last 2 decades it has been shown that a technically correct pediatric ACL reconstruction has little risk in creating clinically significant growth abnormalities. Animal experiments support this hypothesis despite the fact that the gained knowledge cannot be fully generalized to humans. More long time follow-up is needed to fully understand the complete risk factors related to ACL surgery with open growth plates.

Electronic supplementary material

The online version of this article (doi:10.1186/s40634-015-0027-z) contains supplementary material, which is available to authorized users.

Deconstructing the Anterior Cruciate Ligament: What We Know and Do Not Know About Function, Material Properties, and Injury Mechanics

Anterior cruciate ligament (ACL) injury is a common and potentially catastrophic knee joint injury, afflicting a large number of males and particularly females annually. Apart from the obvious acute injury events, it also presents with significant long-term morbidities, in which osteoarthritis (OA) is a frequent and debilitative outcome. With these facts in mind, a vast amount of research has been undertaken over the past five decades geared toward characterizing the structural and mechanical behaviors of the native ACL tissue under various external load applications. While these efforts have afforded important insights, both in terms of understanding treating and rehabilitating ACL injuries; injury rates, their well-established sex-based disparity, and long-term sequelae have endured. In reviewing the expanse of literature conducted to date in this area, this paper identifies important knowledge gaps that contribute directly to this long-standing clinical dilemma. In particular, the following limitations remain. First, minimal data exist that accurately describe native ACL mechanics under the extreme loading rates synonymous with actual injury. Second, current ACL mechanical data are typically derived from isolated and oversimplified strain estimates that fail to adequately capture the true 3D mechanical response of this anatomically complex structure. Third, graft tissues commonly chosen to reconstruct the ruptured ACL are mechanically suboptimal, being overdesigned for stiffness compared to the native tissue. The net result is an increased risk of rerupture and a modified and potentially hazardous habitual joint contact profile. These major limitations appear to warrant explicit research attention moving forward in order to successfully maintain/restore optimal knee joint function and long-term life quality in a large number of otherwise healthy individuals.

Nonanatomic anterior cruciate ligament reconstruction with double-stranded semitendinosus grafts in children with open physes: minimum 15-year follow-up

BACKGROUND

Nonanatomic anterior cruciate ligament (ACL) reconstruction (ACLR) with double-stranded semitendinosus grafts in children with open physes has been described as a successful surgical technique in short-term follow-up clinical reports.

PURPOSE

To evaluate the clinical outcomes of nonanatomic ACLR in children with open physes and a minimum of 15 years' follow-up.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twelve patients with an average age of 10.7 years (range, 8.3-12.4 years) underwent ACLR between 1991 and 1998. All patients were classified as Tanner development stage 2 or lower. The surgical technique involved transphyseal tibial tunnel drilling and over-the-top (OTT) femoral fixation using a double-stranded graft for all patients. Clinical outcomes were evaluated in terms of the manual Lachman test, pivot-shift test, return to sports activity, and International Knee Documentation Committee (IKDC) score at the end of growth and at a minimum 15-year follow-up (range, 15-22 years).

RESULTS

No clinically significant growth disturbance was observed. Ten patients had a grade A IKDC score, and 2 patients had a grade B IKDC score at the end of growth. There was no progression of laxity or modification of knee stability with growth. Three patients (25%) had ACL reruptures during sports activities after growth plate closure. All patients with reruptured ACLs underwent additional reconstructive surgery.

CONCLUSION

Anterior cruciate ligament reconstruction using the OTT technique in the femur and the transphyseal technique in the tibia produces good results with regard to growth plate closure but a high failure rate in adulthood.

Effects of suture choice on biomechanics and physeal status after bioenhanced anterior cruciate ligament repair in skeletally immature patients: a large-animal study

PURPOSE

The objective of this study was to assess the effect of absorbable or nonabsorbable sutures in bioenhanced anterior cruciate ligament (ACL) repair in a skeletally immature pig model on suture tunnel and growth plate healing and biomechanical outcomes.

METHODS

Sixteen female skeletally immature Yorkshire pigs were randomly allocated to receive unilateral, bioenhanced ACL repair with an absorbable (Vicryl) or nonabsorbable (Ethibond) suture augmented by an extracellular matrix-based scaffold (MIACH). After 15 weeks of healing, micro-computed tomography was used to measure residual tunnel diameters and growth plate status, and biomechanical outcomes were assessed.

RESULTS

At 15 weeks postoperatively, there was a significant difference in tunnel diameter with significantly larger diameters in the nonabsorbable suture group (4.4 ± 0.3 mm; mean ± SD) than in the absorbable group (1.8 ± 0.5 mm; P < .001). The growth plate showed a significantly greater affected area in the nonabsorbable group (15.2 ± 3.4 mm(2)) than in the absorbable group (2.7 ± 0.8 mm(2), P < .001). There was no significant difference in the linear stiffness of the repairs (29.0 ± 14.8 N/mm for absorbable v 43.3 ± 28.3 N/mm for nonabsorbable sutures, P = .531), but load to failure was higher in the nonabsorbable suture group (211 ± 121.5 N) than in the absorbable suture group (173 ± 101.4 N, P = .002). There was no difference between the 2 groups in anteroposterior laxity at 30° (P = .5117), 60° (P = .3150), and 90° (P = .4297) of knee flexion.

CONCLUSIONS

The use of absorbable sutures for ACL repair resulted in decreased physeal plate damage after 15 weeks of healing; however, use of nonabsorbable sutures resulted in 20% stronger repairs.

CLINICAL RELEVANCE

Choice of suture type for ACL repair or repair of tibial avulsion fractures may depend on patient skeletal age and size, with absorbable sutures preferred in very young, small patients at higher risk with physeal damage and nonabsorbable sutures preferred in larger, prepubescent patients who may place higher loads on the repair.

Biomechanical and histological evaluations of the doubled semitendinosus tendon autograft after anterior cruciate ligament reconstruction in sheep

BACKGROUND

A sheep or goat anterior cruciate ligament (ACL) reconstruction model with the semitendinosus tendon autograft has not as of yet been established.

HYPOTHESIS

The semitendinosus tendon graft may be necrotized after ACL reconstruction until 12 weeks. Structural properties of the femur-graft-tibia complex may not be restored to the normal ACL level even at 12 months after surgery.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-eight mature sheep were used. In each animal, the right knee underwent ACL reconstruction using the semitendinosus tendon autograft. Two of them were not tested because of pneumonia. Twenty of 36 sheep were used for biomechanical evaluations. Five randomly selected animals were sacrificed at 0, 12, 24, or 52 weeks after surgery. In each animal, both the knees were harvested, and the left knee was used to obtain the control data. The remaining 16 sheep were used for histological evaluation. Two or 3 randomly selected animals were sacrificed at 0, 2, 6, 12, 24, or 52 weeks after surgery.

RESULTS

The tendon graft was predominantly acellular at 2 weeks. Although cell infiltration increased at 6 weeks, the core portion remained necrotic even at 12 weeks. At 24 and 52 weeks, the necrotic lesion disappeared in the core portion. In each period, the anteroposterior translation of the reconstructed knee remained significantly greater than that of the control (P < .0001). At 52 weeks, the maximum load of the femur-graft-tibia complex was significantly lower than that of the femur-ACL-tibia complex (P < .0001), although there was no significant difference in the cell density, the tissue dimensions, the stiffness, and the elongation at failure between the 2 complexes.

CONCLUSION

The sheep ACL reconstruction model showed predominant intrinsic fibroblast necrosis in the tendon autograft until 12 weeks. Although the structural properties of the femur-graft-tibia complex gradually improved, they were not completely restored to the femur-ACL-tibia complex level even at 52 weeks.

CLINICAL RELEVANCE

Remodeling of the semitendinosus tendon autograft after ACL reconstruction is not different from that of the bone-tendon-bone graft. This study has suggested that vigorous activity should not be permitted for patients in the early periods after ACL reconstruction using semitendinosus tendon autografts, which are necrotized and weakened after surgery.

Three-dimensional engineered bone-ligament-bone constructs for anterior cruciate ligament replacement

The anterior cruciate ligament (ACL), a major stabilizer of the knee, is commonly injured. Because of its intrinsic poor healing ability, a torn ACL is usually reconstructed by a graft. We developed a multi-phasic, or bone-ligament-bone, tissue-engineered construct for ACL grafts using bone marrow stromal cells and sheep as a model system. After 6 months in vivo, the constructs increased in cross section and exhibited a well-organized microstructure, native bone integration, a functional enthesis, vascularization, innervation, increased collagen content, and structural alignment. The constructs increased in stiffness to 52% of the tangent modulus and 95% of the geometric stiffness of native ACL. The viscoelastic response of the explants was virtually indistinguishable from that of adult ACL. These results suggest that our constructs after implantation can obtain physiologically relevant structural and functional characteristics comparable to those of adult ACL. They present a viable option for ACL replacement.