The "ligamentization" process in human anterior cruciate ligament reconstruction with autogenous patellar and hamstring tendons: a biochemical study

Arthroscopic Coracoclavicular Ligament Reconstruction Using a Synthetic Polycaprolactone-Based Polyurethane Urea Tendon Graft: A Report of 5 Cases

BACKGROUND

Several techniques have been introduced to treat acromioclavicular (AC) separation using the semitendinosus tendon as a graft for coracoclavicular (CC) ligament reconstruction. However, the tendon may have been used previously or the patient may not want it harvested. Hence, synthetic tendon transfers have become increasingly popular.

METHODS

Five patients with chronic AC separations were treated. A synthetic polyurethane urea tendon graft (Artelon Tissue Reinforcement [ATR]) was chosen for its ability to partially transform into connective tissue. The patient follow-up period lasted 45 to 60 months.

RESULTS

The mean preoperative Constant Score increased from 64.8 to 100 postoperatively. The mean preoperative Simple Shoulder Test increased from 7.2 to 12 postoperatively. The mean postoperative increase of the CC distance was 1.5 mm. The mean expansion of the clavicular drill hole from the original was 2.1 mm. According to the postoperative magnetic resonance imaging, the grafts had healed well and the cross-sections of the grafts were up to 10.5 mm between the coracoid and the clavicle.

DISCUSSION

The synthetic ATR tendon strip was a practical method for reconstructing a torn CC ligament complex. The ATR graft appears promising for future CC ligament reconstructions.

The ACL injury response: A collagen-based analysis

BACKGROUND

Anterior cruciate ligament (ACL) injuries do not effectively heal. Tendon graft tissue after reconstruction shows rapid tissue turnover and 'ligamentization.' It is unknown whether native torn ACL tissue undergoes significant collagen turnover after injury or is arrested by the intraarticular environment. It is also unknown whether injury mechanism or chronicity affect torn ligament tissue turnover.

METHODS

Thirty-three mid-substance ACL biopsies were obtained during primary arthroscopic ACL reconstruction (n=31; nine contact injuries, 22 non-contact injuries, 22 males, 11 females; mean age 28.5 years; median injury to surgery time 12 weeks), or from cadavers as uninjured ACL (n=2). As a marker for collagen turnover, immature collagen cross-link content was determined by ninhydrin reagent assays. The immature cross-link content was assessed against injury mechanism, patient age, and injury to surgery time. Histochemical analysis was conducted on two uninjured ACL cadaveric controls, a four-week-old ACL tear, and a four-year-old ACL tear.

RESULTS

Contact and non-contact groups were not demographically different with respect to sex, patient age, injury to surgery time, and activity involvement prior to injury, which ranged from basketball to logging. Collagen crosslink content was very low across all samples, suggesting high tissue turnover between injury and surgery regardless of injury mechanism (non-contact: 1.68ng/mol, CI 0.48-2.89; contact: 1.50ng/mol, CI 0.14-2.86; p=0.842).

CONCLUSION

Collagen turnover occurs rapidly after ACL injury regardless of contact or non-contact mechanism. Robust tissue turnover starts within the first several weeks after injury and persists to some extent throughout the life of the torn ACL.

Role of Physiotherapy in Preventing Failure of Primary Anterior Cruciate Ligament Reconstruction

Background/Purpose

Anterior cruciate ligament (ACL) reconstruction is routinely performed in sports medicine. We aimed to determine if there is any protective effect of postoperative physiotherapy in preventing graft rupture after primary ACL reconstruction (ACLR).

Methods

A retrospective case—control study was carried out, with demographic data, concomitant meniscal injury, and intraoperative fixation methods matched. The number of sessions of physiotherapy attended by the rupture group and nonrupture group were compared using binary logistic regression.

Results

No significant relationship between the frequency of postoperative physiotherapy and occurrence of graft rupture after primary ACLR was identified.

Conclusion

Further research is needed to verify the effect of physiotherapy in the prevention of graft rupture after primary ACLR.

Is Remnant Preservation Truly Beneficial to Anterior Cruciate Ligament Reconstruction Healing? Clinical and Magnetic Resonance Imaging Evaluations of Remnant-Preserved Reconstruction

BACKGROUND

Remnant-preserved anterior cruciate ligament (ACL) reconstruction was introduced to improve clinical outcomes and biological healing. However, the effects of remnant preservation and the influence of the delay from injury until reconstruction on the outcomes of this technique are still uncertain. Purpose/Hypothesis: The purposes of this study were to evaluate whether remnant preservation improved the clinical outcomes and graft incorporation of ACL reconstruction and to examine the influence of the delay between ACL injury and reconstruction on the usefulness of remnant preservation. We hypothesized that remnant preservation improves clinical results and accelerates graft incorporation and that its effect is dependent on the delay between ACL injury and reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 151 consecutive patients who underwent double-bundle ACL reconstruction using a semitendinosus graft were enrolled in this study: 74 knees underwent ACL reconstruction without a remnant (or the remnant was <25% of the intra-articular portion of the graft; NR group), while 77 knees underwent ACL reconstruction with remnant preservation (RP group). These were divided into 4 subgroups based on the time from injury to surgery: phase 1 was <3 weeks (n = 24), phase 2 was 3 to less than 8 weeks (n = 70), phase 3 was 8 to 20 weeks (n = 32), and phase 4 was >20 weeks (n = 25). Clinical measurements, including KT-1000 arthrometer side-to-side anterior tibial translation measurements, were assessed at 3, 6, 12, and 24 months after reconstruction. Magnetic resonance imaging evaluations of graft maturation and graft-tunnel integration of the anteromedial and posterolateral bundles were assessed at 3, 6, and 12 months after reconstruction.

RESULTS

There was no difference in side-to-side anterior tibial translation between the NR and RP groups. There was also no difference in graft maturation between the 2 groups. Furthermore, the time from ACL injury until reconstruction did not affect graft maturation, except in the case of very long delays before reconstruction (phase 4). Graft-tunnel integration was significantly increased in both groups in a time-dependent manner. However, there was no difference between the NR and RP groups.

CONCLUSION

Remnant preservation did not improve knee stability at 2 years after ACL reconstruction. Furthermore, remnant preservation did not accelerate graft incorporation, especially during the acute and subacute injury phases.

Anterior cruciate ligament reconstruction: principles of treatment

Anterior cruciate ligament (ACL) reconstruction is one of the most common procedures in sports medicine. Several areas of controversy exist in ACL tear management which have engaged surgeons and researchers in debates towards identifying an ideal approach for these patients.

This instructional review discusses the principles of ACL reconstruction in an attempt to provide guidelines and initiate a critical thinking approach on the most common areas of controversy regarding ACL reconstruction.

Using high-level evidence from the literature, as presented in randomised controlled trials, systematic reviews, and meta-analyses, operative versus conservative treatment, timing of surgery, and rehabilitation are discussed. Also, the advantages and disadvantages of the most common types of autografts, such as patellar tendon and hamstrings as well as allografts are presented.

Key considerations for the anatomical, histological, biomechanical and clinical data (‘IDEAL’) graft positioning are reviewed.

Cite this article: Paschos NK, Howell SM. Anterior cruciate ligament reconstruction: principles of treatment. EFORT Open Rev 2016;398-408. DOI: 10.1302/2058-5241.1.160032.

[Biodegradable synthetic polymers for the design of implantable medical devices: the ligamentoplasty case]

The sector of implantable medical devices is a growing sector of health products especially dynamic in the field of research. To improve the management of patients and to meet clinical requirements, researchers are developing new types of medical devices. They use different families of biomaterials presenting various chemical and physical characteristics in order for providing clinicians with health products optimized for biomedical applications. In this article, we aim to show how, starting from a family of biomaterials (degradable polymers), it is possible to design an implantable medical device for the therapeutic management of the failure of anterior cruciate ligament. The main steps leading to the design of a total ligament reinforcement are detailed. They range from the synthesis and characterization of degradable polymer to the shaping of the knitted implant, through the assessment of the study of the impact of sterilization on mechanical properties and checking cytocompatibility.

Relationship between bony tunnel and knee function in patients after patellar dislocation triple surgeries-a CT-based study

We aimed to assess the CT-based bony tunnel valuations and their correlation with knee function after patellar dislocation triple surgeries. A retrospective study was performed on 66 patients (70 knees) who underwent patellar dislocation triple surgeries. The surgery was MPFL reconstruction primarily, combined with lateral retinaculum release and tibial tubercle osteotomy. CT examinations were performed to determine the femoral tunnel position, along with the patellar and femoral tunnel width 3 days and more than 1 year after operation for follow-up. Functional evaluation based on Kujala and Lysholm scores was also implemented. We compared tunnel width of the first and last examinations and correlated femoral tunnel position of the last examination with knee function. At the last follow-up, femoral tunnel position in the anterior-posterior direction was moderately correlated with knee function. Femoral tunnel position in the proximal-distal direction was not associated with postoperative knee function. Patellar and femoral tunnel width increased significantly at the last follow-up. However, no significant functional difference was found between patients with and without femoral tunnel enlargement. Our results suggested that the tunnel malposition in anterior-posterior position based on CT was related to impaired knee function during the follow-ups.

Bracing can partially limit tibial rotation during stressful activities after anterior crucial ligament reconstruction with a hamstring graft

BACKGROUND

Hamstring graft has substantial differences with BPTB graft regarding initial mechanical strength, healing sequence, and vascularization, which may imply that a different approach during rehabilitation period is required. The purpose of this study was to investigate the influence of knee bracing on tibial rotation in ACL-reconstructed patients with a hamstring autograft during high loading activities. The hypothesis was that there would be a decrease in tibial rotation in the ACL-reconstructed braced knee as compared to the unbraced knee.

METHODS

Twenty male patients having undergone unilateral ACL reconstruction with a semitendinosus/gracilis autograft were assessed. Kinematic data were collected with an eight-camera optoelectronic system during two stressful tasks: (1) descending from a stair and subsequent pivoting; and (2) landing from a platform and subsequent pivoting. In each patient, three different experimental conditions were evaluated: (A) wearing a prophylactic brace (braced condition); (B) wearing a patellofemoral brace (sleeved condition); (C) without brace (unbraced condition). The intact knee without brace served as a control.

RESULTS

Tibial rotation was significantly lower in the intact knee compared to all three conditions of the ACL-reconstructed knee (P≤0.01 for both tasks). Presence of a brace or sleeve resulted in lower tibial rotation than in the unbraced condition (p=0.003 for descending/pivot and P=0.0004 for landing/pivot). The braced condition resulted in lower rotation than the sleeved condition for descending/pivoting (P=0.031) while no differences were found for landing/pivoting (P=0.230).

CONCLUSION

Knee bracing limited the excessive tibial rotation during pivoting under high loading activities in ACL-reconstructed knees with a hamstring graft. This partial restoration of normal kinematics may have a potential beneficial effect in patients recovering from ACL reconstruction with a hamstring autograft.

LEVEL OF EVIDENCE

Level III, case-control therapeutic study.

The difference in clinical outcome of single-bundle anterior cruciate ligament reconstructions with and without remnant preservation: A meta-analysis

BACKGROUND

The aim of this study was to compare the clinical performance and complications between an ACL reconstruction with a remnant-preserving single-bundle technique and a standard single-bundle technique.

METHODS

A search was performed of RCTs comparing the clinical outcomes and complications of ACL reconstruction with remnant-preserving and standard single-bundle techniques during October 2014. Relevant data were extracted and CONSORT was used to assess the methodological quality. Stata/SE 12.0 was used to perform a meta-analysis of the clinical outcomes.

RESULTS

Six RCTs were included, with a total of 378 patients: 190 in the remnant-preservation technique group and 188 patients in standard-technique group. Assessing anterior stability, no difference was found between the groups for the KT arthrometer, negative rate of Lachman, and the pivot shift test. Assessing functional outcome, there was no significant difference in IKCD scores and grades or Lysholm score. In terms of complications, the percentage of tibial tunnel enlargement in the group of the remnant-preservation technique was significantly lower, despite no significant difference in the incidence of cyclops lesions.

CONCLUSIONS

The outcome of single-bundle ACL reconstruction with the remnant-preservation technique is similar to that with the standard technique in terms of anterior stability and functional recovery of the knee. Remnant preservation in ACL reconstruction decreases the percentage of tibial tunnel enlargement. Level of evidence is II.

Comparison of Graft Failure Rate Between Autografts Placed via an Anatomic Anterior Cruciate Ligament Reconstruction Technique: A Systematic Review, Meta-analysis, and Meta-regression

BACKGROUND

Recent data from the Danish anterior cruciate ligament (ACL) registry demonstrated increased reoperation rates for hamstring tendon autografts when an anatomic ACL reconstruction is performed. This is consistent with reports of greater time needed for hamstring tendon autografts to mature compared with other autografts.

PURPOSE

To review the literature comparing graft failure rate between patellar and hamstring tendon autografts placed anatomically and to determine if there are differences in return to preinjury activity levels between autografts.

STUDY DESIGN

Systematic review with meta-analysis and meta-regression.

METHODS

The PubMed, MEDLINE, SPORTDiscus, and CINAHL databases were used to identify studies published from January 1, 2000, through March 7, 2014. To compare postoperative outcomes between patellar tendon and hamstring tendon autografts, summary event rates for graft failure and return to preinjury activity level were calculated. A meta-analysis was performed to calculate a summary odds ratio (OR) for graft failure between autografts using the studies that directly compared the 2 autografts. Meta-regression analyses were performed to assess the influence of postoperative follow-up time on graft failure rate.

RESULTS

A total of 28 studies reported graft failures for patellar tendon (6 studies) and hamstring tendon (26 studies) autografts used with anatomic ACL reconstruction; 4 of the 28 were comparison studies. Graft failure rate was not significantly different between patellar tendon (7.0% [95% CI, 4.6%-10.5%]) and hamstring tendon autografts (3.9% [95% CI, 2.7%-5.6%]). The odds of graft failure were slightly higher for hamstring tendon autografts (OR, 1.21 [95% CI, 0.63-2.33]), but this difference was not significant (P = .57). The rate of patients returning to preinjury activity levels was not significantly different between patellar (n = 1 study; 58.1% [95% CI, 40.4%-73.9%]) and hamstring tendon autografts (n = 5 studies; 75.6% [95% CI, 43.7%-92.5%]). Overall graft failure rate was positively associated with postoperative follow-up time, but this effect was only significant with hamstring tendon autografts (P < .05).

CONCLUSION

Differences in graft failure rate between patellar tendon and hamstring tendon autografts were not significant. Although follow-up time was only found to have a significant influence on hamstring tendon graft failure rates, this was likely due to the smaller sample of studies assessing patellar tendon graft failures. Differences in return to preinjury activity levels could not be determined due to the lack of studies assessing that outcome. Both patellar and hamstring tendon autografts demonstrate a low risk of failure and moderately high return to activity level after anatomic ACL reconstruction.

Quantitative and Qualitative Change of Collagen of Achilles Tendons in Rats With Systemic Administration of Glucocorticoids

BACKGROUND

It is unclear whether glucocorticoid (GC) therapy is directly related to Achilles tendon rupture (ATR), because many of the reported patients were receiving long-term GC therapy for underlying diseases. This study aimed to elucidate the mechanism by which systemic GC administration causes weakening of the Achilles tendon by biochemically, mechanically, and morphologically evaluating quantitative and qualitative changes in collagen.

METHODS

Male 8-week-old mice were subcutaneously treated with either prednisolone (10 mg/mL/kg; GC group) or saline (1 mL/kg; control group) for 8 weeks and then subjected to the following experiments: (1) a tensile strength test; (2) quantification of the gene expressions of type 1 collagen and lysyl oxidase; (3) quantification of collagen content, enzymatic crosslinks (immature + mature), and senescent crosslinks; and (4) measurement of collagen fiber diameter by electron microscopy.

RESULTS

The maximum tensile load and gene expressions of type 1 collagen and lysyl oxidase were decreased in the GC group. Collagen content was significantly decreased in the GC group compared with the control group. The content of enzymatic crosslinks was significantly lower in the GC group than in the control group. The corresponding amount of senescent crosslinks was not significantly different. The mean collagen fiber diameter was significantly smaller in the GC group than in the control group. Histogram analysis showed a decreased number of thick fibers and an increased number of thin fibers in the GC group.

CONCLUSION

These observations suggest that systemic GC administration causes decreased strength of the Achilles tendon by decreasing its collagen content, hindering the formation of enzymatic crosslinks and thereby keeping collagen fibers in an immature state with smaller diameters.

CLINICAL RELEVANCE

This animal study showed that systemic GC administration directly prevents maturation of tendon collagen fibers and decreases tendon strength, regardless of the presence or absence of underlying disease.

RISKS AND CONSEQUENCES OF USING THE TRANSPORTAL TECHNIQUE IN RECONSTRUCTING THE ANTERIOR CRUCIATE LIGAMENT: RELATIONSHIPS BETWEEN THE FEMORAL TUNNEL, LATERAL SUPERIOR GENICULAR ARTERY AND LATERAL EPICONDYLE OF THE FEMORAL CONDYLE

Objective: Define a security zone to avoid possibles vascular and ligamentar complications during anterior cruciate ligament reconstruction. Methods: Arthroscopic reconstruction using the transtibial and transportal technique in cadaver knees was performed followed by dissection and measurement of the distance between the femoral tunnel and the proximal attachment of the lateral collateral ligament and the femoral tunnel and the lateral superior genicular artery. Results: The measure of the analysed distances show us an aproximation between the major branch of the lateral superior genicular artery and the femoral insertion of the colateral lateral ligament and the femoral tunnel during the transportal technique. Conclusion: We realize that the use of technical ship it to arthroscopic ACL reconstruction has a higher probability of injury to the lateral geniculate artery and insertion of the lateral collateral ligament, promoting post-surgical complications such as instability of the knee, osteonecrosis of the femoral condyle and ligamentização graft.

Anatomic Placement of the Femoral Tunnels in Double-Bundle Anterior Cruciate Ligament Reconstruction Correlates With Improved Graft Maturation and Clinical Outcomes

PURPOSE

To compare maturation of reconstructed graft on second-look arthroscopy and clinical outcomes between 2 groups: the provisional anatomic (PA) group, with both the anteromedial (AM) and posterolateral (PL) femoral tunnels in their anatomic location, and the nonanatomic (NA) group, with either 1 of the 2 femoral tunnels beyond its anatomic location after double-bundle anterior cruciate ligament reconstruction.

METHODS

We enrolled 154 patients who underwent 3-dimensional computed tomography scanning and second-look arthroscopy after double-bundle anterior cruciate ligament reconstruction. All of the patients were divided into the PA and NA groups according to the femoral tunnel position determined by the quadrant method. Graft maturation was evaluated with 3 subsections, including integrity, tension, and synovial coverage with revascularization, on second-look arthroscopy. We also compared Lachman test, pivot-shift test, KT-2000 (MEDmetric, San Diego, CA), and International Knee Documentation Committee grades at the last follow-up.

RESULTS

Of the 154 patients, 88 were classified as the PA group and 66 as the NA group by the quadrant method. A difference existed between groups for the AM tunnel position but not for the PL tunnel position. The PA group showed a higher graft maturation score (P < .001 for all comparisons) and better results according to the International Knee Documentation Committee knee rating, Lachman test, pivot-shift test, and KT-2000 assessment (P < .001 for all comparisons).

CONCLUSIONS

The PA group with anatomic femoral tunnel placement showed a higher graft maturation score on second-look arthroscopy, along with better clinical outcomes, than the NA group. There was a significant difference in the AM femoral tunnel position but not in the PL tunnel position between the 2 groups.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Tendon Graft Healing in Multiligament Reconstructed Knee Detected by FDG-PET/CT: A Pilot Study

Background and Aims:

The detection of graft viability is challenging in the multiligament reconstructed knee. Magnetic resonance imaging gives structural information but lacks the capability to assess biological activity of the grafts. 18F-labeled fluorodeoxyglucose positron emission tomography combined with computer tomography is shown to be a sensitive method for imaging tissue metabolism and viability. The aim of the present study was to evaluate the feasibility of fluorodeoxyglucose positron emission tomography combined with computer tomography imaging in the detection of the replacement graft metabolism in multiligament reconstructed knees.

Materials and Methods:

Seven patients (17–44 years) with multiligament reconstructed knee underwent fluorodeoxyglucose positron emission tomography combined with computer tomography to evaluate the biological activity of replacement grafts. The degree of fluorodeoxyglucose uptake reported as standard uptake values from the region of interest was analyzed 3–24 months postoperatively.

Results:

In all patients, the fluorodeoxyglucose positron emission tomography combined with computer tomography showed increased fluorodeoxyglucose uptake in all replacement grafts at different follow-up time points. Furthermore, fluorodeoxyglucose was higher at femoral condyles of operated knees compared to contralateral reference values.

Conclusion:

This pilot study shows a significant increase in tendon graft metabolism during two first years of postoperative healing. The fluorodeoxyglucose positron emission tomography combined with computer tomography imaging seems to be adequate method of assessment of graft metabolism and viability during postoperative healing. The clinical value of fluorodeoxyglucose positron emission tomography combined with computer tomography imaging, however, warrants further evaluation with longitudinal studies with a larger patient population.

Effects of Collagen Crosslinking on Bone Material Properties in Health and Disease

Data have accumulated to show that various types of collagen crosslinking are implicated in the health of individuals, as well as in a number of disease states, such as osteoporosis, diabetes mellitus, chronic kidney disease, inflammatory bowel disease, or in conditions of mild hyperhomocysteinemia, or when glucocorticoid use is indicated. Collagen crosslinking is a posttranslational modification of collagen molecules and plays important roles in tissue differentiation and in the mechanical properties of collagenous tissue. The crosslinking of collagen in the body can form via two mechanisms: one is enzymatic crosslinking and the other is nonenzymatic crosslinking. Lysyl hydroxylases and lysyl oxidases regulate tissue-specific crosslinking patterns and quantities. Enzymatic crosslinks initially form via immature divalent crosslinking, and a portion of them convert into mature trivalent forms such as pyridinoline and pyrrole crosslinks. Nonenzymatic crosslinks form as a result of reactions which create advanced glycation end products (AGEs), such as pentosidine and glucosepane. These types of crosslinks differ in terms of their mechanisms of formation and function. Impaired enzymatic crosslinking and/or an increase of AGEs have been proposed as a major cause of bone fragility associated with aging and numerous disease states. This review focuses on the effects of collagen crosslinking on bone material properties in health and disease.

Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model

Introduction

The anterior cruciate ligament (ACL) injury is one of the most common in the knee. Tendons can be used as alternative grafts for ACL repair, with tendon “ligamentization” often reported in literature. The purpose of this study was to evaluate the morphological and histological changes occurring in a semitendinosus tendon (ST) during ACL reconstruction in growing rabbits.

Materials and methods

Twenty-one 8-week-old New Zealand white rabbits, weighing about 1500 g underwent reconstructive surgery on the right knee. In two cases the left knee was used to verify the normal microstructure of the ACL and ST in rabbits. The rabbits were then randomly divided into seven groups and sacrificed at 1, 4, 6, 8, 12, 24 and 48 weeks after surgery. The specimens were evaluated under light microscopy to analyze the changes in the intra-articular tract of the graft. The evidence of necrosis, neovascularization and organization of the collagen fibers were investigated.

Results

One month after surgery, numerous disorganized fibroblasts and collagenous fibers were identified. A marked reduction of cellular necrosis was observed in the early phase of the neo-ligament healing process. After 4 weeks, these fusiform-like cells became more rounded. By 8 weeks, the collagen fibers had become aligned in parallel with newly formed capillaries and highly differentiated fibroblasts. At 24 and 48 weeks the transplanted tendon differed histologically from both tendon and ligament.

Conclusions

The data of the present study showed that ligamentization did not occur until at least 24 months post-operatively and, during healing, the grafted tendon assumed a unique micro-architecture that was a middle between a tendon and a ligament.

The ACL reconstruction in pediatric age has become more frequent in these past recent years. The use of semitendinosus graft with preservation of its distal attachment should be the gold standard in skeletally immature patients.

Does Gracilis Tendon Harvest During ACL Reconstruction with a Hamstring Autograft Affect Torque of Muscles Responsible for Shin Rotation?

Background

A growing body of evidence indicates that in patients after anterior cruciate ligament reconstruction (ACLR) with a combined semitendinosus and gracilis (STGR) graft there are large deficits in the internal rotation strength, which has led some authors to recommend harvest of only ST tendon whenever possible. The purpose of this study was to assess the isometric (IT) and peak torque (PT) of the muscles responsible for shin rotation in patients after ACLR with an ST or with an STGR graft.

Material/Methods

Twenty patients with an ST graft and 20 patients with a combined STGR graft underwent a 6-month postoperative rehabilitation program after ACLR. At the end of the rehabilitation program, the IT and PT of the muscles responsible for internal (IR) and external rotation (ER) of the shin were measured. The results were compared to the results of a control group. Additionally, to determine the reliability of the dynamometer for clinical research, a test-retest assessment was performed.

Results

There were no statistically significant differences between the 3 groups of participants. Nevertheless, in the STGR group there was a statistically significant difference between the IT of muscles internally rotating the shin in the involved knee and uninvolved knee at 25° of the internal shin rotation.

Conclusions

Comparison of IT and PT measurements performed after 24 weeks of postoperative rehabilitation generally showed no differences between patients after ACLR with the use of ST graft and patients who received a combination graft consisting of STGR. Nevertheless, there was an influence of GR harvest on internal shin rotation torque at a deep internal rotation angle.

Tripeptide-copper complex GHK-Cu (II) transiently improved healing outcome in a rat model of ACL reconstruction

After anterior cruciate ligament reconstruction (ACLR), the biological healing of the graft is a rate-limiting step which can contribute to graft failure. The tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu(II) (GHK-Cu) is a well-known activator of tissue remodeling. We investigated whether GHK-Cu can improve graft healing following ACLR. Seventy-two rats underwent unilateral ACLR were randomized to saline, 0.3 or 3 mg/ml GHK-Cu groups (n = 24). Post-operational intra-articular injections were given from week 2, once a week, for 4 weeks. Gait analysis was performed pre-injury and at harvesting time. At 6 or 12 weeks post-operation, knee specimens were harvested for knee laxity test, graft pull-out test, and histology. At 6 weeks post-ACLR, GHK-Cu groups resulted in a smaller side-to-side difference in knee laxity as compared to the saline group (p = 0.009), but there was no significant difference at 12 weeks post-operation. The graft complex in the 0.3 mg/ml GHK-Cu group had higher stiffness than saline group at 6 weeks post-operation (p = 0.026), but there was no significant difference in ultimate load, gait parameters, and histological scores among treatment groups. All grafts failed mid-substance during pull-out test. Intra-articular supplementation with a bioactive small molecule GHK-Cu improved graft healing following ACLR in rat, but the beneficial effects could not last as treatment discontinued.

Tissue engineering of ligaments for reconstructive surgery

PURPOSE

The use of musculoskeletal bioengineering and regenerative medicine applications in orthopaedic surgery has continued to evolve. The aim of this systematic review was to address tissue-engineering strategies for knee ligament reconstruction.

METHODS

A systematic review of PubMed/Medline using the terms "knee AND ligament" AND "tissue engineering" OR "regenerative medicine" was performed. Two authors performed the search, independently assessed the studies for inclusion, and extracted the data for inclusion in the review. Both preclinical and clinical studies were reviewed, and the articles deemed most relevant were included in this article to provide relevant basic science and recent clinical translational knowledge concerning "tissue-engineering" strategies currently used in knee ligament reconstruction.

RESULTS

A total of 224 articles were reviewed in our initial PubMed search. Non-English-language studies were excluded. Clinical and preclinical studies were identified, and those with a focus on knee ligament tissue-engineering strategies including stem cell-based therapies, growth factor administration, hybrid biomaterial, and scaffold development, as well as mechanical stimulation modalities, were reviewed.

CONCLUSIONS

The body of knowledge surrounding tissue-engineering strategies for ligament reconstruction continues to expand. Presently, various tissue-engineering techniques have some potential advantages, including faster recovery, better ligamentization, and possibly, a reduction of recurrence. Preclinical research of these novel therapies continues to provide promising results. There remains a need for well-designed, high-powered comparative clinical studies to serve as a foundation for successful translation into the clinical setting going forward.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

Distinctive collagen maturation process in fibroblasts derived from rabbit anterior cruciate ligament, medial collateral ligament, and patellar tendon in vitro

PURPOSE

Differences in the tissue-specific collagen maturation process between tendon and ligament are still unknown. Collagen cross-link formation is crucial for the collagen maturation process. The aim of this study is to examine collagen maturation processes of anterior cruciate ligament (ACL), medial collateral ligament (MCL), and patellar tendon (PT) in vitro, in order to determine the optimal cell source for tissue engineering of ligament.

METHODS

Cells derived from the ACL, MCL, and PT of New Zealand white rabbits were isolated. Each cell type was cultured for up to 4 weeks after reaching confluence. Cell-matrix layers were evaluated and compared for their morphology, collagen cross-links, and gene expression levels of lysine hydroxylase 1 and 2, lysyl oxidase (LOX), tenomodulin, collagen1A1 (Col1A1), and collagen3A1 (Col3A1).

RESULTS

Transmission electron microscopy photomicrographs verified that collagen fibrils were secreted from all three types of fibroblasts. A higher ratio of dihydroxylysinonorleucine/hydroxylysinonorleucine was evident in the ligament compared to the tendon, which was consistent with lysine hydroxylase 2/lysine hydroxylase 1 gene expression. The gene expression of LOX, which regulates the total amount of enzymatic cross-linking, and the gene expression levels of Col1A1 and Col3A1 were higher in the ACL matrix than in the MCL and PT matrices.

CONCLUSION

ACL, MCL, and PT cells have distinct collagen maturation processes at the cellular level. In addition, the collagen maturation of ACL cells is not necessarily inferior to that of MCL and PT cells in that all three cell types have a good ability to synthesize collagen and induce collagen maturation. This bioactivity of ACL cells in terms of ligament-specific mature collagen induction can be applied to tissue-engineered ACL reconstruction or remnant preserving procedure with ACL reconstruction.

Prospective comparisons of femoral tunnel enlargement with 3 different postoperative immobilization periods after double-bundle anterior cruciate ligament reconstruction with hamstring grafts

PURPOSE

To determine the effect of differing postoperative immobilization periods on femoral bone tunnel enlargement and clinical outcome after double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring grafts.

METHODS

Fifty-one patients undergoing primary double-bundle ACL reconstruction with hamstring grafts were divided into 3 postoperative immobilization protocol groups: 2-day immobilization with the knee in 20° of flexion postoperatively (group A, n = 18); 1-week immobilization (group B, n = 17); and 2-week immobilization (group C, n = 16). Bone tunnel enlargement was determined by computed digital radiographs taken on the first postoperative day and at 24 months in the anteroposterior (AP) and lateral views. Each tunnel diameter was shown as a percentage of the maximum joint width of the proximal tibia on the AP view or a percentage of the maximum diameter of the patella on the lateral view. To determine the incidence of tunnel enlargement, a percentage diameter change of more than 10% was defined as an enlarged tunnel. The standard clinical evaluation was also performed. This study used nonrandomized procedures.

RESULTS

In each group there were no significant differences in the incidence and magnitude of anteromedial and posterolateral bone tunnel enlargement on both the AP and lateral views (1-factor analysis of variance). Group C showed significantly less muscle strength in knee extension compared with the contralateral knee (85.3% ± 18.4%) than group A (93.7% ± 13.1%, P = .049) and group B (96.8% ± 12.9%, P = .044).

CONCLUSIONS

This prospective radiographic study showed that femoral bone tunnel enlargement, in both the anteromedial and posterolateral tunnels, may occur after double-bundle ACL reconstruction with hamstring grafts despite different postoperative immobilization periods, with no significant difference in the incidence and magnitude among groups with differing postoperative immobilization periods. In addition, a 2-week immobilization period after surgery showed harmful effects, such as significantly less quadriceps muscle strength.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Regional mechanical properties of human patellar tendon allografts

PURPOSE

Very little is known regarding regional biomechanical properties of patellar tendon allografts.

METHODS

Ten human bone-tendon-bone (BTB) patellar grafts were separated into equal thirds and underwent cyclic and failure testing. Grafts were non-irradiated and processed using proprietary sterilization methods.

RESULTS

The central third was the thickest region (4.9 ± 0.4 mm) compared to the medial and lateral (p < 0.05). The lateral third was the longest region (58.8 ± 8.8 mm) compared to the medial (47.9 ± 8.5 mm) and central (47.2 ± 8.8 mm) portions (p < 0.05). Cyclic testing demonstrated no regional differences with respect to elongation (n.s.) and creep strain (n.s.). Failure testing demonstrated increased maximum load and stiffness in the central region (1,680 ± 418 N and 278 ± 67 N/mm, respectively) as compared to the medial (1,033 ± 214 N, p < 0.002, 201 ± 37 N/mm, p < 0.03) and lateral thirds (908 ± 412 N, p < 0.03, 173 ± 66 N/mm, p < 0.002). Elongation at maximum load did not vary between regions. Central region maximum stress (41.0 ± 12.5 MPa) was greater than that of the medial third (28.1 ± 3.6 MPa, p < 0.02), with strain at maximum stress larger in the central third (0.21 ± 0.03) compared to lateral (0.16 ± 0.03, p < 0.01).

CONCLUSIONS

The central third of a non-irradiated, human bone-patellar tendon-bone construct is thicker and biomechanically superior to the medial and lateral regions in most respects. These findings reinforce the use of the central third of a patellar tendon allograft in anterior cruciate ligament reconstruction. Further investigations are required to determine whether the decreased biomechanical properties of the medial and lateral third of the BTB construct negatively influence the mechanical function of hemi-BTB grafts.

Hamstring tendon autograft versus LARS artificial ligament for arthroscopic posterior cruciate ligament reconstruction in a long-term follow-up

INTRODUCTION

Surgical reconstruction has been increasingly recommended for the surgical management of posterior cruciate ligament (PCL) ruptures. While the choice of tissue graft still remains controversial. Currently both hamstring tendon autograft (HTG) and ligament advanced reinforcement system (LARS) artificial ligament are widely used but there are seldom reports on the comparisons of their clinical results. Our study was aimed to assess the effectiveness of these two grafts.

MATERIALS AND METHODS

Thirty-five patients with unilateral PCL rupture were enrolled in this retrospectively study. Sixteen of them received arthroscopically assisted PCL reconstruction using hamstring tendon autografts (HTG group) and nineteen using LARS ligaments (LARS group). All cases were followed up for 46-57 months with a mean of 51 months. Follow-up examinations included radiographic assessment, Lysholm score, Tegner score, International Knee Documentation Committee (IKDC) rating scales and KT-1000 test.

RESULTS

All patients improved significantly at the final follow-up compared with the examinational results preoperatively and there were no significant differences between HTG group and LARS group with respect to the results of radiographic assessment, Lysholm score, Tegner score, IKDC rating scales and KT-1000 test.

CONCLUSIONS

Similar good clinical results were obtained after PCL reconstruction using hamstring tendon autografts and LARS ligaments. Both LARS ligament and hamstring tendon autograft are ideal grafts for PCL reconstruction.

Intra-articular remodelling of hamstring tendon grafts after anterior cruciate ligament reconstruction

PURPOSE

A summary is provided on the existing knowledge about the specific healing phases of the intra-articular hamstring tendon graft used for ACL reconstruction. Differences between human and animal in vivo studies are explained, and implications for the postoperative time period are laid out.

METHODS

A systematic review of the existing literature was performed on the topic of tendon remodelling of hamstring grafts in ACL reconstruction using Medline database. Publications between 1982 and 2012 were included. Special focus was directed on in vivo human and animal studies analysing intra-articular free tendon graft remodelling.

RESULTS

Animal and human in vitro and vivo researches have demonstrated three characteristic stages of graft healing after ACL reconstruction: an early graft healing phase with central graft necrosis and hypocellularity and no detectable revascularization of the graft tissue, followed by a phase of proliferation, the time of most intensive remodelling and revascularization and finally, a ligamentization phase with characteristic restructuring of the graft towards the properties of the intact ACL. However, a full restoration of either the biological or biomechanical properties of the intact ACL is not achieved.

CONCLUSION

Significant knowledge on human cruciate ligament remodelling has been added in the understanding of the processes during the course of graft healing. Most importantly, the remodelling process in humans is prolonged compared to animal studies. While today´s rehabilitation protocols are often extrapolated from findings of animal in vivo healing studies, current findings of human in vivo healing studies might require new post-operative regimens following hamstring ACL reconstruction.

"Ligamentization" in hamstring tendon grafts after anterior cruciate ligament reconstruction: a systematic review of the literature and a glimpse into the future

PURPOSE

The aims of this study were to provide a systematic review of the literature on "ligamentization" in hamstring tendon (HT) grafts after anterior cruciate ligament (ACL) reconstruction and analyze the postoperative remodeling process in human patients and animal models.

METHODS

We performed a search in the Medline, PubMed, Embase and The Cochrane Library databases, followed by a manual search of reference lists to identify relevant articles. Only studies that investigated the ligamentization of hamstring grafts by histologic examination and comprehensively reported on the remodeling process were deemed eligible for review.

RESULTS

A total of 4 studies were determined appropriate for systematic review: 2 of the included studies investigated human ACL grafts and 2 were performed in animal models. The studies included the examination of 79 human hamstring graft biopsy specimens and grafts of 27 skeletally mature sheep. To verify the remodeling process, authors reported on various aspects of cellularity, vascularity, and collagen organization. None of the included studies reached a level of evidence higher than 3.

CONCLUSIONS

A postoperative ligamentization process can be found in HT grafts after ACL reconstruction and shows a typical progression through 3 distinguishable remodeling phases in humans and in animal models, whereas the progression and intensity of remodeling is distinctly increased in animals.

CLINICAL RELEVANCE

Because postoperative remodeling influences biomechanical properties of hamstring grafts, a better understanding of this process and its timing could lead to substantial improvements in postoperative care strategies and indirectly to the optimization of surgical techniques.

Platelet-rich plasma: does it help reduce tunnel widening after ACL reconstruction?

PURPOSE

The purpose of this study was to evaluate the efficacy of platelet-rich plasma (PRP) in reducing femoral and tibial tunnel enlargement in patients operated on for anterior cruciate ligament reconstruction with hamstrings.

METHODS

Forty male patients, in which both femoral and tibial 9-mm tunnels were performed because of the graft size, were enrolled in this prospective study. They were randomly assigned to group A (20 patients, PRP group) and group B (20 patients, control group). All patients were followed up at a median of 14.7 months (range 10-16 months), with a physical examination, the Tegner, Lysholm and objective IKDC scoring scales, and with the KT-1000 arthrometer. Moreover, they underwent a CT evaluation in order to assess the amount of tunnel enlargement.

RESULTS

Femoral tunnel diameter increased from 9.0 ± 0.1 mm to 9.8 ± 0.3 mm in group A (p = 0.032) and from 9.0 ± 0.1 mm to 9.4 ± 0.5 mm in group B (p = 0.043). Tibial tunnel diameter increased from 9.0 ± 0.2 mm to 10.9 ± 0.2 mm in group A (p = 0.029) and from 9.1 ± 0.1 mm to 10.1 ± 0.4 mm in group B (p = 0.028). Physical examination as well as the evaluation scales used showed no differences between the two groups.

CONCLUSIONS

The use of PRP does not seem to be effective in preventing tunnel enlargement.

The use of layer by layer self-assembled coatings of hyaluronic acid and cationized gelatin to improve the biocompatibility of poly(ethylene terephthalate) artificial ligaments for reconstruction of the anterior cruciate ligament

In this study layer by layer (LBL) self-assembled coatings of hyaluronic acid (HA) and cationized gelatin (CG) were used to modify polyethylene terephthalate (PET) artificial ligament grafts. Changes in the surface properties were characterized by scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and contact angle and biomechanical measurements. The cell compatibility of this HA-CG coating was investigated in vitro on PET films seeded with human foreskin dermal fibroblasts over 7days. The results of our in vitro studies demonstrated that the HA-CG coating significantly enhanced cell adhesion, facilitated cell growth, and suppressed the expression of inflammation-related genes relative to a pure PET graft. Furthermore, rabbit and porcine anterior cruciate ligament reconstruction models were used to evaluate the effect of this LBL coating in vivo. The animal experiment results proved that this LBL coating significantly inhibited inflammatory cell infiltration and promoted new ligament tissue regeneration among the graft fibers. In addition, the formation of type I collagen in the HA-CG coating group was much higher than in the control group. Based on these results we conclude that PET grafts coated with HA-CG have considerable potential as substitutes for ligament reconstruction.

The outcome at 15 years of endoscopic anterior cruciate ligament reconstruction using hamstring tendon autograft for 'isolated' anterior cruciate ligament rupture

The purpose of this study was to report the outcome of 'isolated' anterior cruciate ligament (ACL) ruptures treated with anatomical endoscopic reconstruction using hamstring tendon autograft at a mean of 15 years (14.25 to 16.9). A total of 100 consecutive men and 100 consecutive women with 'isolated' ACL rupture underwent four-strand hamstring tendon reconstruction with anteromedial portal femoral tunnel drilling and interference screw fixation by a single surgeon. Details were recorded pre-operatively and at one, two, seven and 15 years post-operatively. Outcomes included clinical examination, subjective and objective scoring systems, and radiological assessment. At 15 years only eight of 118 patients (7%) had moderate or severe osteo-arthritic changes (International Knee Documentation Committee Grades C and D), and 79 of 152 patients (52%) still performed very strenuous activities. Overall graft survival at 15 years was 83% (1.1% failure per year). Patients aged < 18 years at the time of surgery and patients with > 2 mm of laxity at one year had a threefold increase in the risk of suffering a rupture of the graft (p = 0.002 and p = 0.001, respectively). There was no increase in laxity of the graft over time. ACL reconstructive surgery in patients with an 'isolated' rupture using this technique shows good results 15 years post-operatively with respect to ligamentous stability, objective and subjective outcomes, and does not appear to cause osteoarthritis.

The reharvested patellar tendon has the potential for ligamentization when used for anterior cruciate ligament revision surgery

PURPOSE

The aim of the present study was to make an in-depth clinical, radiographical, and histological evaluation of patients who underwent anterior cruciate ligament (ACL) revision surgery with reharvested central third patellar tendon autograft.

METHODS

Four patients (two women and two men) underwent ACL revision surgery with reharvested patellar tendon autograft 71 (66-120) months after the primary reconstruction. The patients were followed prospectively and underwent a clinical examination and magnetic resonance imaging (MRI) at two and 10 years. Furthermore, they underwent a second-look arthroscopy involving a biopsy procedure from the reconstructed ACL 3 years after revision surgery.

RESULTS

The clinical results were poor both at two and 10 years, but the knees were stable and had a firm endpoint in all four patients in the Lachman test. At the second-look arthroscopy, the graft appeared macroscopically normal in all four patients. Histologically two patients had a normal or close to normal appearance of the reconstructed ACL with no or slight increase in cellularity and vascularity. Two patients had a marked increase in cellularity and vascularity, and the findings revealed that ligamentization was present in all four patients.

CONCLUSIONS

The clinical outcome 10 years after ACL revision surgery was poor in these four patients. In contrast, the reharvested patellar tendon appeared close to normal on MRI, and the second-look arthroscopy with the concomitant histological findings revealed that the grafts were viable 3 years after revision. Therefore, the reharvested patellar tendon seems to have the potential for ligamentization when used for ACL revision surgery.

LEVEL OF EVIDENCE

Case series, Level IV.

Graft-dependent differences in the ligamentization process of anterior cruciate ligament grafts in a sheep trial

PURPOSE

The structural properties of the healing ligament are the determining factor for the stability of the reconstruction before, during, and after osseous integration of anterior cruciate ligament grafts. Over the course of ligamentization, the stability of synovialized grafts seems lower than that of non-synovialized patellar tendon grafts.

METHODS

In an animal study on 42 sheep, 21 non-synovialized grafts (patellar tendon) and 21 synovialized grafts (flexor digitorum superficialis tendon) were performed to replace the anterior cruciate ligament. After 6, 12, and 24 weeks, 7 animals from each group were euthanized and investigated. Anteroposterior stability of the knee was assessed. After removal of all other soft tissues, the ACL was loaded to failure. Histology and histological analysis of the intra-articular graft region was then performed.

RESULTS

There were no significant differences in the translation test comparing synovialized and non-synovialized grafts. After 6, 12, and 24 weeks, all transplants failed in the tensile test due to interligamentous rupture or avulsion. After 6 weeks, transplants did not show significant biomechanical differences. Load to failure and stiffness of the patellar tendon was more than twice those of synovialized tendon (P = 0.002) after 12 weeks. Histology revealed necrosis in patellar tendon specimens after 12 weeks. A significant increase in load to failure was determined in synovialized ligament grafts between 12 and 24 weeks (P = 0.005). Its load capacity then tended to be higher than that of patellar tendon grafts.

CONCLUSION

The stability of synovialized ligament grafts is significantly lower than that of non-synovialized patellar tendon grafts after 12 weeks. This difference is compensated after 24 weeks. The significantly lower load to failure of synovialized compared with non-synovialized grafts after 12 weeks may be clinically relevant for the rehabilitation process of anterior cruciate ligament grafts in humans.

Anterior cruciate ligament strain and tensile forces for weight-bearing and non-weight-bearing exercises: a guide to exercise selection

There is a growing body of evidence documenting loads applied to the anterior cruciate ligament (ACL) for weight-bearing and non-weight-bearing exercises. ACL loading has been quantified by inverse dynamics techniques that measure anterior shear force at the tibiofemoral joint (net force primarily restrained by the ACL), ACL strain (defined as change in ACL length with respect to original length and expressed as a percentage) measured directly in vivo, and ACL tensile force estimated through mathematical modeling and computer optimization techniques. A review of the biomechanical literature indicates the following: ACL loading is generally greater with non-weight-bearing compared to weight-bearing exercises; with both types of exercises, the ACL is loaded to a greater extent between 10° to 50° of knee flexion (generally peaking between 10° and 30°) compared to 50° to 100° of knee flexion; and loads on the ACL change according to exercise technique (such as trunk position). Squatting with excessive forward movement of the knees beyond the toes and with the heels off the ground tends to increase ACL loading. Squatting and lunging with a forward trunk tilt tend to decrease ACL loading, likely due to increased hamstrings activity. During seated knee extension, ACL force decreases when the resistance pad is positioned more proximal on the anterior aspect of the lower leg, away from the ankle. The evidence reviewed as part of this manuscript provides objective data by which to rank exercises based on loading applied to the ACL. The biggest challenge in exercise selection post-ACL reconstruction is the limited knowledge of the optimal amount of stress that should be applied to the ACL graft as it goes through its initial incorporation and eventual maturation process. Clinicians may utilize this review as a guide to exercise selection and rehabilitation progression for patients post-ACL reconstruction.

Sparing the anterior cruciate ligament remnant: is it worth the hassle?

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is the most common surgically treated ligament injury. Many efforts have been taken to reconstruct it as anatomically as possible to restore knee stability and, possibly, prevent knee osteoarthritis.

SOURCES OF DATA

A literature search was performed using the isolated or combined keywords 'ACL augmentation remnant', 'ACL reconstruction and remnant and stump', 'ACL reconstruction and remnant and stump preserving and stability' and 'ACL remnant complete tear' with no limit regarding the year of publication. We identified seven published studies.

AREAS OF AGREEMENT

The ACL remnant might accelerate the vascularization and the ligamentization of the graft and contribute to faster graft innervation leading to a better proprioception.

AREAS OF CONTROVERSY

The role of the ACL remnant is debated, because, although it may increase the risk of impingement and the formation of cyclops lesion, its preservation can improve proprioception, biomechanical functions and vascularity. However, the current assessment methods to assess proprioception, vascularization and the ligamentization do not lead to hard evidence that preservation of the remnant confers clinically relevant advantages over its excision.

GROWING POINTS

The ACL remnant has been demonstrated in experimental studies to have a role in improving revascularization, ligamentization and reinnervation of the graft, but these findings are still not supported by clinical findings. A more direct way to assess proprioceptive function after ACL reconstruction and appropriately conducted powered and rigorously prospective randomized double-blind studies comparing the clinical outcomes of excising the remnant to leaving it in situ are necessary.

The "ligamentization" process in anterior cruciate ligament reconstruction: what happens to the human graft? A systematic review of the literature

BACKGROUND

Surgical anterior cruciate ligament reconstruction using tendon grafts has become the standard to treat the functionally unstable anterior cruciate ligament-deficient knee. Although tendons clearly differ biologically from ligaments, multiple animal studies have shown that the implanted tendons indeed seem to remodel into a ligamentous "anterior cruciate ligament-like" structure.

PURPOSE

The goal of this study was to systematically review the current literature on the "ligamentization" process in human anterior cruciate ligament reconstruction.

STUDY DESIGN

Systematic review.

METHODS

A computerized search using relevant search terms was performed in the PubMed, MEDLINE, EMBASE, and Cochrane Library databases, as well as a manual search of reference lists. Searches were limited to studies examining the healing of the intra-articular portion of the tendon graft based on biopsies of this graft obtained from a living human.

RESULTS

Four studies were determined to be appropriate for systematic review, none of them reaching a level of evidence higher than 3. All reports considered autografts. Biopsy specimens were evaluated by light or electron microscopy and analyzed for vascularization, cellular aspects, and appearance of extracellular matrix. All authors universally agreed that the tendon grafts survive in the intra-articular environment. Based on changes observed in the healing grafts with regard to vascularization, cellular aspects, and properties of the extracellular matrix, different chronologic stages in the ligamentization process were discerned.

CONCLUSION

The key finding of this systematic review is that a free tendon graft replacing a ruptured human anterior cruciate ligament undergoes a series of biologic processes termed "ligamentization." The graft seems to remain viable at any time during this course. Histologically, the mature grafts may resemble the normal human anterior cruciate ligament, but ultrastructural differences regarding collagen fibril distribution do persist. Different stages of the ligamentization process are described, but no agreement exists on their time frame. Problematic direct transmission of animal data to the human situation, the limited number of reports considering the ligamentization process in humans, and the potential biopsy sampling error attributable to superficial graft biopsies necessitate further human studies on anterior cruciate ligament graft ligamentization.

Anterior cruciate ligament reconstruction using remnant preservation and a femoral tensioning technique: clinical and magnetic resonance imaging results

PURPOSE

The purpose of this study was to investigate the clinical and magnetic resonance imaging (MRI) results of anterior cruciate ligament (ACL) reconstruction with autogenous hamstring tendon by use of remnant preservation and a femoral tensioning technique.

METHODS

A total of 53 patients who had ACL reconstruction by use of remnant ACL stump preservation and a femoral tensioning technique were evaluated. Clinical evaluation at a minimum of 2 years after surgery included range of motion, Lachman test, pivot-shift test, KT-2000 arthrometer testing (MEDmetric, San Diego, CA), and clinical scores. Plain radiographs were evaluated for tunnel enlargement. MRI was obtained for evaluation of graft continuity, cyclops-like mass lesion, and positioning of the tibial tunnel. Second-look arthroscopy was performed in 33 patients.

RESULTS

The clinical scores improved postoperatively. There were statistically significant differences between preoperative and postoperative Lachman tests, pivot-shift tests, and KT-2000 arthrometer measurements. Postoperative MRI was available in 48 patients, and it showed intact graft in 45 patients, 2 partial tears, and 1 complete loss of graft. There were cyclops-like mass lesions in 12 patients, but none showed an extension limitation or pain at extension. The position of the tibial tunnel on the sagittal and coronal view was similar to the position of the normal ACL tibial insertion. The measured tibial tunnel widening on the radiographs at final follow-up was 2.2 ± 1.5 mm.

CONCLUSIONS

Reconstruction of the ACL by use of preservation and femoral tensioning of the remnant tissue showed good clinical results without increased concerns regarding incorrect tunnel formation. Postoperative MRI showed an increased incidence of cyclops-like mass lesions, but no clinical significance was observed.

LEVEL OF EVIDENCE

Level IV, case series.

Revascularization process of the bone--patellar tendon--bone autograft evaluated by contrast-enhanced magnetic resonance imaging 6 and 12 months after anterior cruciate ligament reconstruction

BACKGROUND

Contrast-enhanced magnetic resonance imaging (MRI) studies conducted on animal models have shown that the observed signal intensity changes are related to the degree of graft vascularity and its biomechanical properties.

PURPOSE

To evaluate by contrast-enhanced MRI the revascularization process at 3 distinct sites discerned in relation to the surrounding microenvironment along the course of bone-patellar tendon-bone (BPTB) autograft in uncomplicated human anterior cruciate ligament (ACL)-reconstructed knees.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-two male patients were assessed with a 3-dimensional fast field echo/short tau inversion recovery (FFE/STIR) MRI sequence at the third postoperative day and at time intervals of 6 and 12 months after surgery. Signal-to-noise quotient (SNQ) was calculated for 3 specific graft sites (intra-articular site, intraosseous tibial tunnel site, and intraosseous juxta screw site) before and after gadolinium administration. Comparisons of the enhancement index (EI: SNQ(after)/SNQ(before) gadolinium) were performed independently for each graft site and time interval.

RESULTS

Three days postoperatively, insufficient vascularization was noticed at the 3 sites. Six and 12 months after surgery, the enhancement index was significantly increased in all 3 sites (P < .001). The intra-articular site, 6 months postoperatively, achieved satisfactory contrast medium uptake (enhancement index >1), with significantly higher enhancement index values compared with the other 2 sites (P < .001). Twelve months after surgery, only the intraosseously enclosed sites displayed an increase of the enhancement index, although nonsignificant (P = .09 and P = .07, respectively).

CONCLUSION

Revascularization of the graft occurs gradually along its length, with the intra-articular site being the first and the faster part to complete this phase, while both the intraosseous sites are still in progress throughout the first postoperative year. Revascularization is an important link at the intrinsic healing chain of the ACL graft. The surrounding microenvironment does seem to play a significant role in this process, and the differences in its composition along the graft course are reflected at the revascularization progress of the corresponding sites.

Single-bundle patellar tendon versus non-anatomical double-bundle hamstrings ACL reconstruction: a prospective randomized study at 8-year minimum follow-up

PURPOSE

The purpose of this study was to compare subjective, objective and radiographic outcome of the lateralized single-bundle bone-patellar tendon-bone autograft with a non-anatomical double-bundle hamstring tendons autograft anterior cruciate ligament (ACL) reconstruction technique at long-term follow-up.

METHODS

Seventy-nine non-consecutive randomized patients (42 men; 37 women) with unilateral ACL insufficiency were prospectively evaluated, before and after ACL reconstruction by means of the above-mentioned techniques, with a minimum follow-up of 8 years (range 8-10 years; mean 8.6 years). In the double-bundle hamstrings technique, we used one tibial and one femoral tunnel combined with one "over-the-top" passage, cortical staple's fixation and we left intact hamstrings' tibial insertion. Patients were evaluated subjectively and objectively, using IKDC score, Tegner level, manual maximum displacement test with KT-2000™ arthrometer. Radiographic evaluation was performed according to IKDC grading system, and re-intervention rate for meniscal lesions was also recorded.

RESULTS

The subjective and objective IKDC were similar in both groups while double-bundle hamstrings group showed significantly higher Tegner level (P = 0.0007), higher passive range of motion recovery (P = 0.0014), faster sport resumption (P = 0.0052), lower glide pivot-shift phenomenon (P = 0.0302) and lower re-intervention rate (P = 0.0116) compared with patellar tendon group. Radiographic evaluation showed significant lower objective degenerative changes in double-bundle hamstrings group at final follow-up (P = 0.0056).

CONCLUSION

Although both techniques provide satisfactory results, double-bundle ACL reconstruction shows better functional results, with a faster return to sport activity, a lower re-operation rate and lower degenerative knee changes.

Remodelling of human hamstring autografts after anterior cruciate ligament reconstruction

PURPOSE

Histological analysis of the remodelling process of human hamstring tendon (HT) grafts after standardized anterior cruciate ligament reconstruction (ACLR) with an accelerated rehabilitation protocol.

METHODS

Sixty-seven patients underwent retrieval of mid-substance biopsies after clinically successful hamstring autograft ACLR. Samples were allocated to one of three groups depending on the time point of retrieval: group 1 (6-12 months; n = 15), group 2 (13-24 months; n = 16) and group 3 (>24 months; n = 11). Biopsies from native HT (n = 17) and ACL (n = 8) served as controls. Cellular density, vascular density and myofibroblast density and collagen fibril alignment were analysed by haematoxylin-eosin, Masson-Goldner-Trichrom and immunohistochemical staining protocols.

RESULTS

Compared with native HT (330.4/mm²), total cell number was increased in groups 1-3 (Group 1 = 482.0/mm² (P = 0.036); group 2 = 850.9/mm² (P = 0.005); and group 3 = 595.6/mm² (P = 0.043). There were no significant differences between the groups for vessel density. Myofibroblast density was higher in group 2 (199.6/mm²) compared with native HT (1.9/mm², P = 0.014). Collagen orientation was irregular up to 12 months. Thereafter, collagen orientation became more regular, adapting to, but not fully restoring, the appearance of the intact ACL. For the first 12 months, cells were predominantly ovoid. Ensuing cell morphology changed to spindle shaped in group 2 and predominantly narrow long cells over 24 months.

CONCLUSION

Human hamstring grafts showed typical stages of graft remodelling, which was not complete up to 2 years after ACLR. The remodelling process in humans was prolonged compared with the results obtained in several animal studies.

LEVEL OF EVIDENCE

Case-control study, Level III.

The effect of platelet-derived growth factors on knee stability after anterior cruciate ligament reconstruction: a prospective randomized clinical study

BACKGROUND

Arthroscopic reconstruction is a standard surgical procedure in cases of symptomatic knee instability due to rupture of the anterior cruciate ligament. Bone-tendon-bone and hamstring tendon grafts are both in use for anterior cruciate ligament reconstruction. There are no significant differences between the two types of graft in relation to function scores, but there is a difference in anteroposterior stability when measured on the KT-2000 arthrometer: knee joints after reconstruction with bone-tendon-bone autografts are more stable than those reconstructed with hamstring tendon autografts.

PURPOSE

To improve knee stability after anterior cruciate ligament reconstruction with a hamstring graft and use of platelet-derived growth factors.

BASIC PROCEDURE

Platelet-leukocyte gel was produced from platelet-leukocyte-rich plasma prepared from a unit of whole blood in an autologous platelet separator. The gel was applied locally, after hamstring graft placement. Fifty patients were included in the study: 25 in the platelet gel group, 25 in a control group. We evaluated anteroposterior knee stability with the KT-2000 arthrometer before surgery and at 3 and 6 months after surgery.

MAIN FINDINGS

Patients treated with the gel demonstrated significantly better anteroposterior knee stability than patients in the control group. The calculated improvements in knee stability at 6 months were 1.3 +/- 1.8 mm in the control group and 3.1 +/- 2.5 mm in the platelet gel group (P = 0.011).

PRINCIPAL CONCLUSION

Platelet-leukocyte gel, applied locally, can improve knee stability in surgery for reconstruction of the anterior cruciate ligament.

Arthroscopic posterior cruciate ligament reconstruction using LARS artificial ligament: a retrospective study

BACKGROUND

The aims of this study were to analyze the preliminary clinical effects of arthroscopic reconstruction of posterior cruciate ligament (PCL) using Ligament Advanced Reinforcement System (LARS) artificial ligament. It is hypothesized that LARS artificial ligament is a safe and effective choice for PCL reconstruction, providing good knee stability.

MATERIALS AND METHODS

Forty-one patients who underwent PCL reconstruction using LARS artificial ligament were enrolled in this retrospective study. Average age at time of surgery was 34 y (range, 23-57 y). Average time from injury to surgery was 15 d (range, 5-45 d). Average follow-up period was 44 mo (range, 36-54 months). Follow-up examinations included the Lysholm Knee Score and the International Knee Documentation Committee (IKDC) score.

RESULTS

The average Lysholm knee score was 64.9 ± 8.8 preoperatively (range, 47-75) versus 92.1 ± 3.3 three years after operation (range, 79-100). Thirty-six of 41 patients (88%) showed good or excellent results at final assessment. The final IKDC score at 3 y postoperatively rated as normal in 21 patients (51%), nearly normal in 17 patients (42%), abnormal in three patients (7%).

CONCLUSIONS

The results shows that LARS artificial ligament appears to be an effective device for PCL reconstruction leading to good ligamentous stability and knee function. Long-term follow-up should be performed to confirm the durable stability of the knee and the tolerance of the knee to the LARS artificial ligament.

Design and characterization of a biodegradable composite scaffold for ligament tissue engineering

Herein we report on the development and characterization of a biodegradable composite scaffold for ligament tissue engineering based on the fundamental morphological features of the native ligament. An aligned fibrous component was used to mimic the fibrous collagen network and a hydrogel component to mimic the proteoglycan-water matrix of the ligament. The composite scaffold was constructed from cell-adherent, base-etched, electrospun poly(epsilon-caprolactone-co-D,L-lactide) (PCLDLLA) fibers embedded in a noncell-adherent photocrosslinked N-methacrylated glycol chitosan (MGC) hydrogel seeded with primary ligament fibroblasts. Base etching improved cellular adhesion to the PCLDLLA material. Cells within the MGC hydrogel remained viable (72 +/- 4%) during the 4-week culture period. Immunohistochemistry staining revealed ligament ECM markers collagen type I, collagen type III, and decorin organizing and accumulating along the PCLDLLA fibers within the composite scaffolds. On the basis of these results, it was determined that the composite scaffold design was a viable alternative to the current approaches used for ligament tissue engineering and merits further study.

Collagen cross-links as a determinant of bone quality: a possible explanation for bone fragility in aging, osteoporosis, and diabetes mellitus

Collagen cross-linking, a major post-translational modification of collagen, plays important roles in the biological and biomechanical features of bone. Collagen cross-links can be divided into lysyl hydroxylase and lysyloxidase-mediated enzymatic immature divalent cross-links,mature trivalent pyridinoline and pyrrole cross-links, and glycation- or oxidation-induced non-enzymatic cross-links(advanced glycation end products) such as glucosepane and pentosidine. These types of cross-links differ in the mechanism of formation and in function. Material properties of newly synthesized collagen matrix may differ in tissue maturity and senescence from older matrix in terms of crosslink formation. Additionally, newly synthesized matrix in osteoporotic patients or diabetic patients may not necessarily be as well-made as age-matched healthy subjects. Data have accumulated that collagen cross-link formation affects not only the mineralization process but also microdamage formation. Consequently, collagen cross-linking is thought to affect the mechanical properties of bone. Furthermore,recent basic and clinical investigations of collagen cross-links seem to face a new era. For instance, serum or urine pentosidine levels are now being used to estimate future fracture risk in osteoporosis and diabetes. In this review, we describe age-related changes in collagen cross-links in bone and abnormalities of cross-links in osteoporosis and diabetes that have been reported in the literature.

Grafted tendon healing in tibial tunnel is inferior to healing in femoral tunnel after anterior cruciate ligament reconstruction: a histomorphometric study in rabbits

PURPOSE

This study aimed to test whether graft healing in the tibial tunnel was inferior to that in the femoral tunnel after anterior cruciate ligament (ACL) reconstruction in rabbits.

METHODS

Surgical reconstruction by use of the digital extensor tendon in the bone tunnel was performed in 18 rabbits. The rabbits were killed at weeks 2, 6, and 12 postoperatively, with 6 at each time point, for histologic examination.

RESULTS

The transiently formed cartilaginous interface was gradually mineralized during re-establishment of direct tendon-to-bone integration, which was observed significantly less in the tibial tunnel than in the femoral tunnel (P < .05). The cell density of the graft was significantly lower in the tibial tunnel than that in the femoral tunnel at weeks 2 and 6 postoperatively (P < .05 for both). An increase in the immature type III collagen content was accompanied by a decrease in graft collagen fiber organization, with healing over time in both the femoral and tibial tunnels. The collagen fiber organization of the graft was significantly poorer in the tibial tunnel than that in the femoral tunnel at week 12 after surgery (P < .05).

CONCLUSIONS

Grafted tendon healing in the tibial tunnel was inferior to that in the femoral tunnel at the tendon-to-bone interface and with regard to the grafted tendon within the bone tunnel after ACL reconstruction in rabbits.

CLINICAL RELEVANCE

Future biopsy study is desirable to test whether this observation was valid clinically, which might provide a scientific basis for therapeutic targets to improve the outcome of ACL surgery.

Tension degradation of anterior cruciate ligament grafts with dynamic flexion-extension loading: a biomechanical model in porcine knees

PURPOSE

This study investigates the influence of various femoral anterior cruciate ligament graft fixation methods on the amount of tension degradation and the initial fixation strength after cyclic flexion-extension loading in a porcine knee model.

METHODS

One hundred twenty porcine digital extensor tendons, used as 4-stranded free tendon grafts, were fixated within porcine femoral bone tunnels by use of extracortical button, cross-pin, or interference screw fixation. One hundred twenty porcine patellar tendon-bone grafts were fixated by use of cross-pin, interference screw, or press-fit fixation. Each femur-graft complex was submitted to cyclic flexion-extension loading for 1,000 cycles throughout different loading ranges, and the total loss of tension was determined. After cyclic testing, the grafts were loaded to failure, and the data were compared with a pullout series without cyclic loading.

RESULTS

Tension degradation after 1,000 cycles of flexion-extension loading averaged 62.6% +/- 10.0% in free tendon grafts and 48.9% +/- 13.35% in patellar tendon-bone grafts. There was no influence of the loading range on the total amount of tension degradation. The total amount of tension degradation was the highest with interference screw fixation of free tendon and patellar tendon-bone grafts. Despite excessive loss of tension, the initial fixation strength of the femur-graft complex was not reduced.

CONCLUSIONS

The method of femoral graft fixation significantly influenced tension degradation during dynamic flexion-extension loading. Femoral graft fixation methods that secure the graft close to the tunnel entrance and that displace the graft substance from the center of the bone tunnel show the largest amount of tension degradation during cyclic flexion-extension loading. The graft substance, not the fixation site, was the weakest link of the graft complex within this investigation.

CLINICAL RELEVANCE

We believe that the graft fixation method should be considered when aiming to improve the precision of femoral graft placement in anterior cruciate ligament reconstruction.

Effect of anterior cruciate ligament injury and reconstruction on proprioceptive acuity of knee rotation in the transverse plane

BACKGROUND

Studies assessing proprioceptive acuity in anterior cruciate ligament (ACL)-deficient knees have only considered proprioception for knee movements in the sagittal plane rather than in the transverse plane (ie, rotation), despite the fact that the ACL plays a critical role in knee rotational stability and that the ACL is injured almost exclusively with a rotation mechanism. Therefore a test of proprioception is needed that involves movements similar to the mechanism of injury, in this case, rotation.

PURPOSE

To determine whether proprioceptive acuity in rotation changes after ACL injury and reconstruction, and to examine differences in proprioceptive acuity, range, laxity, and activity level among injured knees, contralateral knees, and healthy controls.

DESIGN

Cohort study; Level of evidence, 2.

METHODS

Proprioceptive acuity for active knee rotation movements, passive rotation range of motion, anterior knee laxity, and knee function were measured in 20 consecutive participants with unilateral ACL rupture and 20 matched controls. Reconstruction was performed using a single-incision technique with a 4-strand hamstring tendon autograft. Thirty participants (15 control and 15 ACL reconstructed) were retested at 3 months, and 14 with ACL reconstruction were tested at 6 months.

RESULTS

A deficit was found in preoperative knee rotation proprioception compared with healthy controls (P = .031). Three months after reconstruction, there was a significant improvement (P = .049) in proprioceptive acuity, single-plane anterior laxity (P = .01), and self-reported knee function (P = .001). At 3 months after reconstruction, proprioceptive acuity of the ACL-reconstructed knee was correlated with reported activity level (r = .63; P = .021).

CONCLUSION

Knee rotation proprioception is reduced in ACL-deficient participants compared with healthy controls. Three to 6 months after reconstruction, rotation proprioceptive acuity, laxity, and function were improved. While these findings are consistent with a return to previous activity level 6 months after reconstruction, the extent of graft maturation and restoration of kinematics should also inform the decision about return to sport.

Four-strand hamstring tendon autograft versus LARS artificial ligament for anterior cruciate ligament reconstruction

This retrospective study compared the results after anterior cruciate ligament (ACL) reconstruction using a four-strand hamstring tendon graft (4SHG) versus Ligament Advanced Reinforcement System (LARS) artificial ligament in 60 patients between January 2003 and July 2004 with a minimum four-year follow-up. The KT-1000 examination, the International Knee Documentation Committee (IKDC) scoring systems and Lysholm knee scoring scale were used to evaluate the clinical results. The mean side-to-side difference was 2.4 +/- 0.5 mm and 1.2 +/- 0.3 mm in the 4SHG group and LARS group, respectively (P = 0.013). Although other results of ACL reconstruction, measured by IKDC evaluation, Lysholm scores and Tegner scores, showed using a LARS graft clinically tended to be superior to using a 4SHG, there were no significant differences calculated. Our results suggest that four years after ACL reconstruction using a LARS ligament or 4SHG dramatically improves the function outcome, while the patients in the LARS group displayed a higher knee stability than those in the 4SHG group.