Current trends in anterior cruciate ligament reconstruction. Part 1: Biology and biomechanics of reconstruction

Mechanical comparison of biodegradable femoral fixation devices for hamstring tendon graft--a biomechanical study in a porcine model

BACKGROUND

Initial fixation strength is critical for the early post-operative rehabilitation of patients with anterior cruciate ligament reconstructions. However, even the best femoral fixation devices remain controversial. We compared the biomechanical characteristics of tendon grafts fixed by different biodegradable femoral fixation devices following anterior cruciate ligament reconstruction.

METHODS

The Bio-TransFix, Rigidfix, Bioscrew with EndoPearl augmentation and Bioscrew devices were used to fix porcine flexor digitorum profundus tendon grafts in 32 porcine femora. Displacement of each tendon graft was evaluated after cyclic loading testing. Stiffness, ultimate failure load and failure mode of these fixation devices were measured with load-to-failure testing.

FINDINGS

The displacement of the femur-graft-cement complex in response to cyclic loading was lower (P<0.05) for the Bio-TransFix than the Rigidfix, Bioscrew with EndoPearl augmentation, and Bioscrew groups. The fixation stiffness values of the Rigidfix and the Bioscrew were significantly greater (P<0.05) than that of the Bio-TransFix. The ultimate failure load was significantly greater for the Bio-TransFix and the Rigidfix than the Bioscrew with EndoPearl augmentation or the Bioscrew (P<0.05).

INTERPRETATION

The Bio-TransFix provided the least graft displacement under cyclic loading. However, this device gave less stability. The Rigidfix device provided better stability and stiffness of the tendon graft among those fixation devices that showed no significant differences in graft displacement under cyclic loading. However, no single fixation device provided less displacement along with a larger failure load and stiffness in this study.

Graft tensioning in anterior cruciate ligament reconstruction: a systematic review of randomized controlled trials

PURPOSE

The purposes of this study were to (1) perform a systematic review of randomized controlled trials evaluating graft tensioning in anterior cruciate ligament (ACL) reconstruction, and (2) determine the scientific quality of published randomized controlled trials evaluating graft tensioning in ACL reconstruction.

METHODS

The search strategy included a computerized literature search, a citation search, and a manual search of key journals and conference proceedings. Eligible studies were randomized controlled trials evaluating the effect of graft tensioning on the outcomes of ACL reconstruction. Two reviewers independently performed the literature searches. The validity of the trials was scored using the Detsky quality scale. Consensus was achieved by a study committee of 3 investigators.

RESULTS

Five randomized controlled trials met the inclusion criteria. The mean standardized Detsky score was 61.3 +/- 15.2%. Only 2 of the studies scored >or=75%. All trials consisted of autogenous graft sources, with 3 involving a bone-patellar tendon-bone graft, 1 involving a 5-strand semitendinosus-polyester (5STP) graft, and 1 involving a semitendinosus-gracilis-polyester (STGP) graft.

CONCLUSIONS

Based on the evidence in this systematic review, there is a trend that suggests that 80 N of tension is the most effective amount of tension to apply during ACL reconstruction using hamstring-polyester graft sources. For ACL reconstruction using semitendinosus-gracilis or patellar tendon graft sources, there is no clear trend in terms of statistically significant or clinically relevant differences in terms of the amount of applied tension to apply to the graft during graft fixation. We are unable to provide recommendations as to the amount of tension to apply to 4-strand semitendinosus-gracilis autografts without polyester augmentation because there has been no randomized clinical trial conducted to determine the most effective amount of tension to apply when using this graft source.

The effect of parecoxib and indometacin on tendon-to-bone healing in a bone tunnel

Conventional non-steroidal anti-inflammatory drugs (NSAIDs) and newer specific cyclo-oxygenase-2 (cox-2) inhibitors are commonly used in musculoskeletal trauma and orthopaedic surgery to reduce the inflammatory response and pain. These drugs have been reported to impair bone metabolism. In reconstruction of the anterior cruciate ligament the hamstring tendons are mainly used as the graft of choice, and a prerequisite for good results is healing of the tendons in the bone tunnel. Many of these patients are routinely given NSAIDs or cox-2 inhibitors, although no studies have elucidated the effects of these drugs on tendon healing in the bone tunnel.

In our study 60 female Wistar rats were randomly allocated into three groups of 20. One received parecoxib, one indometacin and one acted as a control. In all the rats the tendo-Achillis was released proximally from the calf muscles. It was then pulled through a drill hole in the distal tibia and sutured anteriorly. The rats were given parecoxib, indometacin or saline intraperitoneally twice daily for seven days. After 14 days the tendon/bone-tunnel interface was subjected to mechanical testing.

Significantly lower maximum pull-out strength (p < 0.001), energy absorption (p < 0.001) and stiffness (p = 0.035) were found in rats given parecoxib and indometacin compared with the control group, most pronounced with parecoxib.

SM, Necat H, H. GR. Use of a magnesium-based bone adhesive for flexor tendon-to-bone healing

PURPOSE

Our previous studies in a canine animal model demonstrated that the flexor tendon-to-bone insertion site has a poor capacity to heal. Magnesium-based adhesives have the potential to improve tendon-to-bone healing. Therefore, we hypothesized that magnesium-based bone adhesive (MBA) will improve the tendon-to-bone biomechanical properties initially and in the early period after repair.

METHODS

Flexor digitorum profundus tendons were injured and repaired into bone tunnels in the distal phalanges of dogs. The bone tunnels were either filled with MBA before completing the repair or left empty (control [CTL]). Histologic appearance, tensile properties, range of motion, and bone density were examined at time zero and 21 days after the repair.

RESULTS

There was no histologic evidence of acute inflammation. There appeared to be more mast cells in the MBA group than in the CTL group. Chronic inflammatory infiltrate and fibrosis was slightly higher in the MBA group compared with the CTL group. Tensile properties at time zero were significantly higher in the MBA group compared with the CTL group. However, tensile properties were significantly lower in the MBA group compared with the CTL group at 21 days. Range of motion and bone density were significantly lower in the MBA and CTL groups compared with normal (ie, uninjured) at 21 days; no differences were seen when comparing MBA with CTL.

CONCLUSIONS

We found that the initial biomechanical properties of flexor tendon-to-bone repairs can be improved with MBA. However, MBA use in vivo led to a decrease in the biomechanical properties of the repair. There was no effect of MBA on bone density or range of motion in the early period after repair. Our histologic analysis suggests that the poor healing in the MBA group may have been due to an allergic response or to increased chronic inflammation resulting from the foreign material.

FUNCTIONAL PERFORMANCE AND KNEE LAXITY IN NORMAL INDIVIDUALS AND IN INDIVIDUALS SUBMITTED TO ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

The aim of this study was to analyze the correlation between deficits in the isokinetic peak torque of the knee extensors and flexors with hop tests, postoperative knee laxity and functional scores in normal and ACL- reconstructed subjects with patellar tendon and hamstring tendon autografts. Methods: Sixty male subjects were enrolled and subdivided into three groups: Twenty subjects without knee injuries (GC group) and two groups of 20 subjects submitted to ACL reconstruction with patellar tendon (GTP group) and hamstrings autograft (GTF group). Results: The results showed significant correlation between knee extensors peak torque and performance in the hop tests for GTF and GC groups. There are no significantly correlations between post op knee laxity and Lysholm score compared with the hop tests and peak torque deficits. Concerning the differences between groups, the GTP group showed greater peak torque deficits in knee extensors, worst Lysholm scores and higher percentage of individuals with lower limb symmetry index (ISM) < 90% in both hop tests when compared to the other two groups. Conclusion: It is not recommendable to use only one measurement instrument for the functional evaluation of ACL-reconstructed patients, because significant correlation between peak torque, subject's functional score, knee laxity and hop tests were not observed in all groups.

Trantibial anterior cruciate ligament double bundle reconstruction technique: two tibial bundle in one tibial tunnel

The anterior cruciate ligament (ACL) consists of two functional bundles that behave independently throughout the range of knee motion. Many two-bundle reconstruction techniques have been introduced to restore the function of the two bundles of the ACL. Generally, two femoral and two tibial tunnels are made during the surgery for a two-bundle ACL reconstruction. However, the procedure is technically demanding and time consuming. This paper describes one-tibial-two-femoral ACL double bundle reconstruction technique with a sextuple-stranded hamstring autograft. The anteromedial femoral tunnel is made using transtibial drilling technique and posterolateral femoral tunnel is made using outside-in technique. The two bundles in a single tibial tunnel are separated using biodegradable interference screw. Stable and adequate femoral fixation of the two bundles with a transtibial fixation and bioabsorbable screw can be obtained. This technique is relatively simple, and replicates the anatomy and differential behavior of the two native bundles of ACL more effectively.

Comparative biomechanical study of the Ligament Plate and other fixation devices in ACL reconstruction

The objective of this study was to evaluate and compare the biomechanical properties of the Ligament Plate with other femoral fixation devices. The Ligament Plate and three different femoral fixation devices were used in fixation of 60 porcine femora and harvested porcine tendons. For each fixation device, a porcine graft-tendon complex was used for the simple load-to-failure test and the load-to-failure test after a cyclic loading test, and the maximal failure load was measured. The amount of graft elongation and failure pattern after the cyclic loading test and load-to-failure test were evaluated. In the BioScrew group, the mean maximal failure load in the load-to-failure test and load-to-failure test after a cyclic loading test was significantly lower and significant graft elongation was noted. There were no significant differences between the other groups. The Ligament Plate provided adequate initial fixation power suitable for early rehabilitation.

Isokinetic Dynamometry in Anterior Cruciate Ligament Injury and Reconstruction

The use of isokinetic dynamometry has often been criticised based on the face-validity argument that isokinetic movements poorly resemble the everyday multi-segmented, dynamic activities of human movements. In the anterior cruciate ligament (ACL) reconstruction or deficiency population where muscle deficits are ubiquitous, this review paper has made a case for using isokinetic dynamometry to isolate and quantify these deficits in a safe and controlled manner. More importantly, the usefulness of isokinetic dynamometry, as applied in individuals with ACL reconstruction or deficiency, is attested by its established known-group and convergent validity. Known-group validity is demonstrated by the extent to which a given isokinetic measure is able to identify individuals who could and could not resume pre-morbid athletic or strenuous activities with minimal functional limitations following an ACL injury. Convergent validity is demonstrated by the extent to which a given isokinetic measure closely associates with self-report measures of knee function in individuals with ACL reconstruction. A basic understanding of the measurement properties of isokinetic dynamometry will guide the clinicians in providing reasoned interventions and advancing the clinical care of their clients. Key words: Biomechanics, Knee, Validity

Tibial bone bridge and bone block fixation in double-bundle anterior cruciate ligament reconstruction without hardware: a technical note

Current techniques for tibial graft fixation in four tunnels double bundle (DB) anterior cruciate ligament (ACL) reconstruction are by means of two interference screws or by extracortical fixation with a variety of different implants. We introduce a new alternative tibial graft fixation technique for four tunnels DB ACL reconstruction without hardware. About 3.5 to 5.5 cm bone cylinder with a diameter of 7 mm is harvested from the anteromedial (and posterolateral) tibial bone tunnel (s) with a core reamer. The anteromedial (AM) and posterolateral (PL) hamstring tendon grafts (or alternatively tendon allografts) are looped over an extracortical femoral fixation device and cut in length according to the total femorotibial bone tunnel length. The distal 3 cm of each, the AM- and PL bundle graft are armed with two strong No. 2 nonresorbable sutures and the four suture ends of each graft are tied to each other over the 2 cm wide cortical bone bridge between the tibial AM and PL bone tunnel. In addition the AM- and/or PL bone block which was harvested at the beginning of the procedure is re-impacted into the two tibial bone tunnels. A dorsal splint is used for the first two postoperative weeks and physiotherapy is started the second postoperative day. The technique is applicable for four tunnels DB ACL reconstruction in patients with good tibial bone quality. The strong fixation technique preserves important tibial bone stock and avoids the use of tibial hardware which knows disadvantages. It does increase tendon to bone contact and tendon-to-bone healing and does reduce implant costs to those of a single bundle (SB) ACL reconstruction. Revision surgery may be facilitated significantly but the technique should not be used when bony defects are present. In case of insufficient bone bridge fixation or bone blocks hardware fixation can be applied as usual.

Prospective randomized comparison of double-bundle versus single-bundle anterior cruciate ligament reconstruction

PURPOSE

Biomechanical studies show increased anterior and rotational stability with double-bundle (DB) compared to single-bundle (SB) anterior cruciate ligament (ACL) reconstruction. The aim of this study was to evaluate the clinical results of four-tunnel DB ACL reconstruction.

METHODS

Seventy patients undergoing arthroscopic hamstring ACL reconstruction were prospectively randomized to DB (n = 35) or SB (n = 35) groups. Each bundle fixation was by means of a femoral EndoButton CL and a tibial biodegradable interference screw. Demographic data were comparable between groups, and the average age of all patients was 29 years. The average follow-up was 19 months for both groups and included a history, clinical evaluation with knee scores, and radiographs.

RESULTS

The subjective results were similar in groups. The subjective International Knee Documentation Committee (IKDC) 2000 score was 88 P for DB versus 90 P for SB; the Lysholm score was 90 P for DB versus 93 P for SB; and the Cincinnati knee score was 91 P for DB versus 92 P for SB. The objective IKDC was significantly higher for DB: 78% "A" (P < .000) and 19% "B" compared to 24% "A" and 68% "B" for SB. The average KT-1000 side-to-side difference was 1.0 mm for DB and 1.6 mm for SB (P = .054) and the pivot shift test was negative in 97% for DB (P = .01) and 71% for SB. The range of motion was comparable for both groups.

CONCLUSIONS

Our study shows a significant advantage in anterior and rotational stability as well as objective IKDC for four-tunnel DB ACL reconstruction compared to SB ACL reconstruction. The subjective Cincinnati knee score, the Lysholm score, and the subjective IKDC 2000 did not show any statistical difference for one or the other technique.

LEVEL OF EVIDENCE

Level I, randomized controlled trial.

Double-bundle anterior cruciate ligament reconstruction using hamstring autografts and bioabsorbable interference screw fixation: prospective, randomized, clinical study with 2-year results

BACKGROUND

Conventional anterior cruciate ligament reconstruction techniques have focused on restoration of the anteromedial bundle only, which, however, may be insufficient in restoring the rotational stability of the knee.

HYPOTHESIS

Rotational stability of the knee is better when using a double-bundle technique instead of a single-bundle technique for anterior cruciate ligament reconstruction.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Seventy-seven patients were randomized into 3 different groups for anterior cruciate ligament reconstruction with hamstring tendons: double-bundle with bioabsorbable screw fixation (n = 25), single-bundle with bioabsorbable screw fixation (n = 27), and single-bundle with metallic screw fixation (n = 25). The evaluation methods were clinical examination, KT-1000 arthrometric measurement, and the International Knee Documentation Committee and Lysholm knee scores.

RESULTS

There were no differences between the study groups preoperatively. Seventy-three patients (95%) were available at a minimum 2-year follow-up (range, 24-35 mo). The rotational stability of the knee, as evaluated by the pivot-shift test, was the best in the patients in the double-bundle group. In addition, the patients in the single-bundle groups had more graft failures than those in the double-bundle group. Concerning the anterior stability of the knee as measured with the KT-1000 arthrometer, the group differences were not statistically significant. No significant differences were found between the groups in knee scores.

CONCLUSION

Rotational stability of the knee is better when using the double-bundle technique instead of the single-bundle technique in anterior cruciate ligament reconstruction.

Complications of anterior cruciate ligament reconstruction with bone-patellar tendon-bone constructs: care and prevention

Rupture of the anterior cruciate ligament is a common injury. Correct diagnosis and patient selection, along with proper surgical technique, with careful attention to anatomic graft placement, followed by attention to proper rehabilitation, leads to predictably good to excellent results. This article reviews the recognition and avoidance of complications associated with bone-patellar tendon-bone constructs of anterior cruciate ligament reconstruction.

Femoral tunnel placement in single-bundle anterior cruciate ligament reconstruction: a cadaveric study relating transtibial lateralized femoral tunnel position to the anteromedial and posterolateral bundle femoral origins of the anterior cruciate ligament

BACKGROUND

There is controversy regarding the necessity of reconstructing both the posterolateral and anteromedial bundles of the anterior cruciate ligament.

HYPOTHESIS

A laterally oriented transtibial drilled femoral tunnel replaces portions of the femoral footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Footprints of the anteromedial and posterolateral bundles of the anterior cruciate ligament were preserved on 7 matched pairs (5 female, 2 male) of fresh-frozen human cadaveric femurs (14 femurs total). Each femur was anatomically oriented and secured in a custom size-appropriate, side-matched replica tibia model to simulate transtibial retrograde drilling of a 10-mm femoral tunnel in each specimen. The relationship of the tunnel relative to footprints of both bundles of the anterior cruciate ligament was recorded using a Microscribe MX digitizer. The angle of the femoral tunnel relative to the vertical 12-o'clock position was recorded for all 14 specimens; only 10 specimens were used for footprint measurements.

RESULTS

On average, the 10-mm femoral tunnel overlapped 50% of the anteromedial bundle (range, 2%-83%) and 51% of the posterolateral bundle (range, 16%-97%). The footprint of the anteromedial bundle occupied 32% (range, 3%-49%) of the area of the tunnel; the footprint of the posterolateral bundle contributed 26% (range, 7%-41%). The remainder of the area of the 10-mm tunnel did not overlap with the anterior cruciate ligament footprint. The mean absolute angle of the femoral tunnel as measured directly on the specimen was 48 degrees (range, 42 degrees-53 degrees) from vertical, corresponding to approximately a 10:30 clock face position on a right knee.

CONCLUSION

Anterior cruciate ligament reconstruction using a laterally oriented transtibial drilled femoral tunnel incorporates portions of the anteromedial and posterolateral bundle origins of the native anterior cruciate ligament.

CLINICAL RELEVANCE

A laterally oriented transtibial drilled femoral tunnel placed at the 10:30 position (1:30 for left knees) reconstructs portions of the anteromedial and posterolateral bundles of the anterior cruciate ligament.

Neuromuscular and biomechanical landing performance subsequent to ipsilateral semitendinosus and gracilis autograft anterior cruciate ligament reconstruction

The hamstrings musculature is a vital component of an intricate dynamic knee joint restraint mechanism. However, there is evidence based on research studies suggesting potential deficits to this complex mechanism due to donor site morbidity resulting from harvest of the ipsilateral semitendinosus and gracilis autograft (ISGA) for anterior cruciate ligament reconstruction (ACLR). The purpose of this retrospective research study was to investigate the effects of ISGA ACLR on neuromuscular and biomechanical performance during a single-leg vertical drop landing (VDL), a functional task and associated mechanism of anterior cruciate ligament disruption during physical activity. Fourteen physically active participants 22.5 +/- 4.1 years of age and 21.4 +/- 10.7 months post ISGA ACLR underwent bilateral neuromuscular, biomechanical and isokinetic strength and endurance evaluations matched to 14 control participants by sex, age, height and mass. Kinetic and kinematic data was obtained with 3-D motion analyses utilizing inverse dynamics while performing single-leg VDLs from a height of 30 cm. Integrated surface electromyography (SEMG) assessments of the quadriceps, hamstrings and gastrocnemius musculature were also conducted. Additionally, knee joint flexion strength (60 degrees s(-1)) and endurance (240 degrees s(-1)) measurements were tested via isokinetic dynamometry. No significant differences existed in hip and net summated extensor moments within or between groups. The ISGA ACLR participants recorded significantly decreased peak vertical ground reaction force (VGRF) landing upon the involved lower extremity compared to uninvolved (P = 0.028) and matched (P < 0.0001) controls. Participants having undergone ISGA ACLR also displayed greater peak hip joint flexion angles landing upon the involved lower extremity compared to uninvolved (P = 0.020) and matched (P = 0.026) controls at initial ground contact. The ISGA ACLR group furthermore exhibited increased peak hip joint flexion angles landing upon the involved lower extremity compared to uninvolved (P = 0.019) and matched (P = 0.007) controls at peak VGRF. Moreover, ISGA ALCR participants demonstrated greater peak knee (P = 0.005) and ankle (P = 0.017) joint flexion angles when landing upon the involved lower extremity compared to the matched control at peak VGRF. The ISGA ACLR group produced significantly greater reactive muscle activation of the vastus medialis (P = 0.013), vastus lateralis (P = 0.008) and medial hamstrings (P = 0.024) in the involved lower extremity compared to the matched control. The ISGA ACLR participants also exhibited greater preparatory (P = 0.033) and reactive (P = 0.022) co-contraction muscle activity of the quadriceps and hamstrings landing upon the involved lower extremity compared to the matched control. In addition, the ISGA ACLR group produced significantly less preparatory (P = 0.005) and reactive (P = 0.010) muscle activation of the gastrocnemius in the involved lower extremity compared to the uninvolved control. No significant differences were present in hamstrings muscular strength and endurance. Harvest of the ISGA for purposes of ACLR does not appear to result in significant neuromuscular, biomechanical or strength and endurance deficiencies due to donor site morbidity. However, it is evident that this specific population exhibits unique neuromuscular and biomechanical adaptations aimed to stabilize the knee previously subjected to ACL trauma and safeguard the ISGA ACLR joint. Co-contraction of quadriceps and hamstrings as well as inhibition of gastrocnemius muscle activation may serve to moderate excessive loads exposed to the intra-articular ISGA during single-leg VDLs. Furthermore, greater muscle activation of the hamstrings in conjunction with increased peak hip, knee and ankle joint flexion angles may assist in enhancing acceptance of VGRF transferred through the kinetic chain following single-leg VDLs.

Tunnel positioning of anteromedial and posterolateral bundles in anatomic anterior cruciate ligament reconstruction: anatomic and radiographic findings

BACKGROUND

The interest in double-bundle anterior cruciate ligament (ACL) reconstructions has recently reawakened.

HYPOTHESIS

The center of the femoral posterolateral (PL) bundle and the center of the femoral anteromedial (AM) bundle are not within the same plane and change their orientation throughout passive knee flexion. Additionally, the tibial center of the AM bundle is aligned with the anterior horn of the lateral meniscus and the center of the PL bundle lies at the recommended tibial tunnel position for single-bundle ACL reconstruction reconstruction, 7 to 9 mm anterior to the posterior cruciate ligament.

STUDY DESIGN

Descriptive laboratory study.

MATERIALS

In 20 human cadaveric knees (age range, 45-87 years) the distances from the center of the AM and PL bundle to the articular cartilage were measured. Radiographic analyses were performed using the techniques of Bernard and Hertel at the femur as well as the method by Stäubli and Rauschning at the tibia.

RESULTS

The center of the AM bundle was at a point 5.3 mm ( +/- 0.7) from the roof of the notch and 5.7 mm ( +/- 0.5) from the intercondylar line. The center of the PL bundle is located at 6.5 mm from the shallow cartilage margin and 5.8 mm from the inferior cartilage margin. On the tibia, the center of the AM bundle is aligned with the anterior horn of the lateral meniscus, while the center of the PL bundle was located 11.2 mm ( +/- 1.2) posterior and 4.1 mm ( +/- 0.6) medial to the anterior insertion of the lateral meniscus. Radiographically, the center of the PL bundle is anterior along Blumensaat's line and lower in the femoral notch along the height of the condyles than the center of the AM bundle. At the tibia, the center of the AM bundle is at 30% and the PL bundle is located at 44% using the method of Stäubli and Rauschning.

CONCLUSION

The center of the femoral PL bundle is shallow and inferior to the AM bundle. On the tibia, the AM bundle lies anterior when compared with the typical single-bundle ACL tunnel that reflects the PL bundle.

CLINICAL RELEVANCE

To imitate the anatomy of the intact ACL, it is mandatory to place the tunnels exactly within the femoral origin and tibial insertion of the ACL.

Results of revision anterior cruciate ligament surgery

BACKGROUND

Revision anterior cruciate ligament surgery remains challenging.

PURPOSE

To analyze the authors' experience with revision anterior cruciate ligament surgery and determine the association between stability and functional results.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between 1991 and 2002, 95 of 102 patients who underwent revision anterior cruciate ligament reconstruction at the authors' institution met the criteria for inclusion in the study. Of those, the 63 (66%) who returned for complete clinical and radiologic evaluation (mean follow-up, 72.7 months) formed the study group. Subjective evaluation focused on return to sports, arthritic symptoms, and subjective International Knee Documentation Committee criteria. Clinical evaluation included examination, KT-1000 arthrometer and functional testing, and radiographic analysis of alignment and arthritis.

RESULTS

Based on International Knee Documentation Committee subjective scores and return to sports, results were rated as excellent/good in 45 patients (71%), fair in 6 (10%), and poor in 12 (19%). A grade IA or IIA Lachman and a KT-1000 arthrometer side-to-side difference of <3 mm (32/63 patients) was associated with a good/excellent result (P < .05). The mechanical axis was midline in 78% (49/63 patients). Radiographic arthritis (16 patients, 25%) was associated with duration of instability after primary failure (P < .03). Return to sports occurred in 59% (37/63 patients). Sixteen patients (25%) required a second revision surgery.

CONCLUSION

Revision anterior cruciate ligament surgery allowed approximately 60% of patients to go back to sports, most of them at lower levels than their prerevision function. Instrumented laxity of <3 mm was associated with a better result. Radiographic arthritis was associated with duration of instability symptoms after primary failure. Patients who undergo revision anterior cruciate ligament surgery should be counseled as to the expected outcome and cautioned that this procedure probably represents a salvage situation and may not allow them to return to their desired levels of function.

Clinical outcomes of allograft versus autograft in anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) injuries are the most common complete ligamentous injury to the knee. The optimal graft should be able to reproduce the anatomy and biomechanics of the ACL, be incorporated rapidly with strong initial fixation, and cause low graft-site morbidity. This article reviews the literature comparing the clinical outcomes following allograft and autograft ACL reconstruction and examines current issues regarding graft choice.

Genetic engineering for skeletal regenerative medicine

The clinical challenges of skeletal regenerative medicine have motivated significant advances in cellular and tissue engineering in recent years. In particular, advances in molecular biology have provided the tools necessary for the design of gene-based strategies for skeletal tissue repair. Consequently, genetic engineering has emerged as a promising method to address the need for sustained and robust cellular differentiation and extracellular matrix production. As a result, gene therapy has been established as a conventional approach to enhance cellular activities for skeletal tissue repair. Recent literature clearly demonstrates that genetic engineering is a principal factor in constructing effective methods for tissue engineering approaches to bone, cartilage, and connective tissue regeneration. This review highlights this literature, including advances in the development of efficacious gene carriers, novel cell sources, successful delivery strategies, and optimal target genes. The current status of the field and the challenges impeding the clinical realization of these approaches are also discussed.

Biomaterials and scaffolds for ligament tissue engineering

Tissue engineering has achieved much progress in an attempt to improve and recover impaired functions of tissues and organs. Although many studies have been done, progress for tissue-engineered anterior cruciate ligaments (ACLs) has been slow due to their complex structures and mechanical properties. In this review, the ACL anatomical structure, progresses achieved, material selection, structure design, and future direction have been discussed, while the challenges and requirements from materials and scaffolds are highlighted. There is a considerably huge amount work that needs to be carried out; as such, future direction in ligament tissue engineering is proposed in hope that this review will give information on future ligament tissue engineering.

Effect of transforming growth factor-beta and growth differentiation factor-5 on proliferation and matrix production by human bone marrow stromal cells cultured on braided poly lactic-co-glycolic acid scaffolds for ligament tissue engineering

Tissue engineering of ligaments based on biomechanically suitable biomaterials combined with autologous cells may provide a solution for the drawbacks associated with conventional graft material. The aim of the present study was to investigate the contribution of recombinant human transforming growth factor beta 1 (rhTGF-beta1) and growth differentiation factor (GDF)-5, known for their role in connective tissue regeneration, to proliferation and matrix production by human bone marrow stromal cells (BMSCs) cultured onto woven, bioabsorbable, 3-dimensional (3D) poly(lactic-co-glycolic acid) scaffolds. Cells were cultured for 12 days in the presence or absence of these growth factors at different concentrations. Human BMSCs attached to the suture material, proliferated, and synthesized extracellular matrix rich in collagen type I and collagen III. No differentiation was demonstrated toward cartilage or bone tissue. The addition of rhTGF-beta1 (1-10 ng/mL) and GDF-5 (10-100 ng/mL) increased cell content (p < 0.05), but only TGF-beta1 also increased total collagen production (p < 0.05) and collagen production per cell, which is a parameter indicating differentiation. In conclusion, stimulation with rhTGF-beta1, and to a lesser extent with GDF-5, can modulate human BMSCs toward collagenous soft tissue when applied to a 3D hybrid construct. The use of growth factors could play an important role in the improvement of ligament tissue engineering.

The mid- to long-term results of the anterior cruciate ligament reconstruction with hamstring tendons using Transfix technique

In this study, mid to long-term results of anterior cruciate ligament reconstruction with hamstring tendons and Transfix technique were evaluated. Anterior cruciate ligament (ACL) reconstruction with four-strand hamstring tendon was performed with Transfix technique on 271 (198 males, 73 females; mean age 25.7; 17-52) patients with anterior cruciate ligament ruptures. The patients were followed up with clinical examination, Lysholm and Tegner activity scales, IKDC scoring system, KT-1000 test and radiological examination. The mean follow-up period was 82 (48-100) months; 204 (75%) patients had no subjective complaints. According to the KT-1000 test, only 14 (5%) patients had more than 5 mm laxity postoperatively, whereas, 161 (59%) patients had more than 5 mm laxity preoperatively. In addition to this, only 19 (7%) patients had Lysholm scores less than 80 postoperatively, whereas 154 (57%) patients scored less than 80 preoperatively. When compared with Tegner activity scale, 189 (70%) patients scored<6 preoperatively and only 24 (8%) postoperatively; 78 (29%) patients scored D preoperatively and only 5 (2%) patients scored D postoperatively on the basis of the IKDC scoring system. Our functional results were found to be satisfactory in more than 90% of patients. Commonly seen problems in ACL reconstruction such as inaccurate graft placement and tunnel widening were found to be consistent with the values in relevant literature. However, we demonstrated that the functional results and the stability of the knee were not related with tunnel widening. This study concludes that the reconstruction of ACL with hamstring tendons and the Transfix technique is reasonably successful, safe and causes low morbidity. Furthermore, we believe that proper graft preparation, accurate tunnel placement, notch-plasty, fixation and rehabilitation program are all as important as the choice of graft and fixation material.

Bioactive scaffolds for bone and ligament tissue

Bone and ligament injuries present the greatest challenges in connective tissue regeneration. The design of materials for these applications lies at the forefront of material science and is the epitome of its current ambition. Indeed, its goal is to design and fabricate reproducible, bioactive and bioresorbable 3D scaffolds with tailored properties that are able to maintain their structure and integrity for predictable times, even under load-bearing conditions. Unfortunately, the mechanical properties of today's available porous scaffolds fall short of those exhibited by complex human tissues, such as bone and ligament. The manipulation of structural parameters in the design of scaffolds and their bioactivation, through the incorporation of soluble and insoluble signals capable of promoting cell activities, are discussed as possible strategies to improve the formation of new tissues both in vitro and in vivo. This review focuses on the different approaches adopted to develop bioactive composite systems for use as temporary scaffolds for bone and anterior ligament regeneration.

Biomechanical analysis of femoral tunnel pull-out angles for anterior cruciate ligament reconstruction with bioabsorbable and metal interference screws

BACKGROUND

Fixation strength of metal and bioabsorbable interference screws has not been evaluated while varying the anterior cruciate ligament graft tension angle.

HYPOTHESIS

There is no difference in fixation strength between 2 types of interference screws for anterior cruciate ligament graft fixation while the graft tension angle is varied relative to the femoral tunnel.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-eight anterior cruciate ligament reconstructions were performed using immature porcine femurs stripped of soft tissue and doubled-over porcine flexor digitorum profundus tendon grafts. Specimens were randomized to bioabsorbable or titanium interference screw fixation. Specimens were randomized to one of three pull angles (0 degrees , 30 degrees , 60 degrees ) representing loading at different knee flexion angles (n = 8/group). Reconstructed ligaments were tensioned to 10 N followed by 200 loading cycles between 10 and 150 N and a final failure test. Construct elongation (mm) at 100 and 200 cycles and failure load (N) were analyzed using a 2-way analysis of variance (P < .05).

RESULTS

Screw material interacted significantly with graft tension angle, as the bioabsorbable screw specimens demonstrated significantly greater fixation strength when tensioned at greater angles. Specimens fixed with bioabsorbable screws showed significantly less elongation at both 100 and 200 cycles and significantly greater failure load compared with titanium screws.

CONCLUSION

Bioabsorbable interference screws acutely have increased fixation strength compared with titanium interference screws for anterior cruciate ligament grafts loaded at greater tension angles.

CLINICAL RELEVANCE

The strength of anterior cruciate ligament reconstruction fixation increases with increasing divergence between the tension angle and femoral tunnel, a condition seen when the knee approaches full extension.

Effectiveness of reconstruction of the anterior cruciate ligament with quadrupled hamstrings and bone-patellar tendon-bone autografts: an in vivo study comparing tibial internal-external rotation

BACKGROUND

The 2 most frequently used autografts for anterior cruciate ligament reconstruction are the bone-patellar tendon-bone and the quadrupled hamstrings tendon.

HYPOTHESIS

Hamstring tendon graft is superior to patellar tendon graft in restoring tibial rotation during highly demanding activities because of its superiority in strength and linear stiffness and because it is closer morphologically to the anatomy of the natural anterior cruciate ligament.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

Eleven patients with patellar tendon graft anterior cruciate ligament reconstruction, 11 patients with hamstring tendon graft anterior cruciate ligament reconstruction, and 11 controls were assessed. Kinematic data were collected (50 Hz) with a 6-camera optoelectronic system while the subjects descended stairs and, immediately after, pivoted on their landing leg. The dependent variable examined was the tibial internal-external rotation during pivoting. All patients in both groups were also assessed clinically and with the use of a KT-1000 arthrometer to evaluate anterior tibial translation.

RESULTS

The results demonstrated that reconstructions with either graft successfully restored anterior tibial translation. However, both anterior cruciate ligament reconstruction groups had significantly increased tibial rotation when compared with the controls, whereas no differences were found between the 2 reconstructed groups.

CONCLUSION

The 2 most frequently used autografts for anterior cruciate ligament reconstruction cannot restore tibial rotation to normal levels.

CLINICAL RELEVANCE

New surgical techniques are needed that can better approximate the actual anatomy and function of the anterior cruciate ligament.

Análise da freqüência mediana do sinal eletromiográfico de indivíduos com lesão do ligamento cruzado anterior em exercícios isométricos de cadeia cinética aberta e fechada

Indivíduos com lesão do ligamento cruzado anterior (LCA) possuem importantes alterações funcionais na musculatura periarticular do joelho. Sendo assim, é de suma importância caracterizar tais alterações, bem como enfatizar um efetivo protocolo de reabilitação para esses indivíduos, com conseqüente retorno às atividades físicas. O objetivo deste estudo foi analisar o comportamento da freqüência mediana (Fmed) em indivíduos com lesão do LCA durante contrações isométricas em exercícios de cadeia cinética aberta (CCA) e fechada (CCF). Entre lesados e não lesados, 40 indivíduos realizaram a extensão do joelho através da contração isométrica voluntária máxima (CIVM) nos aparelhos leg extension e leg press a 30°, 60° e 90° de flexão do joelho. Os resultados revelaram valores da Fmed menores para indivíduos com lesão do LCA quando comparados com o membro contralateral e grupo controle em CCA (p < 0,05). Já exercícios em CCF não apresentaram diferença estatística significativa (p > 0,05) na comparação entre os grupos, não evidenciando esse tipo de lesão. Portanto, a Fmed parece ser uma ferramenta eletromiográfica eficaz na caracterização da lesão crônica do LCA. Além disso, exercícios em CCF parecem ser os mais indicados para a reabilitação desses indivíduos.

Human mesenchymal progenitor cell responses to a novel textured poly(L-lactide) scaffold for ligament tissue engineering

Biocompatibility and cell seeding capability of a new cell scaffold made of textured polylactic acid (PLA) fibers was investigated as a new material for tissue engineering of anterior cruciate ligaments (ACL). Adhesion and proliferation of human mesenchymal progenitor cells (MPC) was investigated after 15 days by scanning electron microscopy and standard histology. Expression of collagen type I and III, fibronectin, tenascin C, decorin, smooth muscle actin, and the matrix metalloproteinases MMP-1 and MMP-2, as well as their tissue inhibitors TIMP-1 and TIMP-2 was analyzed using real-time PCR. Protein expression of collagen I and III, tenascin C, and proliferating nuclear antigen (PCNA) was determined by immunohistology. Apoptosis was analyzed by detection of p53 expression and TUNEL staining. MPC seeded the scaffold homogeneously and showed good cell growth and no increased rate of apoptosis. After 15 days, the matrix forming genes collagen type I, tenascin C, and decorin were upregulated, indicating the formation of a ligament-like matrix. MMP-1 and TIMP-1 were also significantly increased, suggesting initial matrix remodeling. It was concluded that the new porous PLA scaffold allowed homogeneous cell seeding, a fibroblastic phenotype and the production of a ligament-like matrix and, therefore, might be a suitable cell carrier for ACL tissue engineering.

Comparison of direct and indirect interference screw fixation for tendon graft in rabbits

For ACL reconstruction, interference screw can fix the graft in the bone tunnel closer to the articular surface. However, direct interference screw fixation has a possibility to damage the tendon graft at the time of screw insertion, and the bone-tendon contact area is limited within the tunnel. To avoid the damage to the tendon graft at the time of screw insertion and to increase the bone-tendon contact area, a free bone plug was interposed between screw and tendon graft (indirect interference screw fixation). The purpose of this study was to compare ultimate load strength and histological findings between two techniques in a rabbit model. Ultimate pull-out load tests and histological examinations were evaluated at time 0, 3 and 6 weeks. The ultimate failure load of indirect interference screw fixation was significantly higher than that of direct interference screw fixation immediately after surgery (P < 0.05). Histologically, the interface tissues between tendon graft and host bone were more organized and matured in indirect technique. These findings showed that indirect interference screw fixation for tendon graft increased fixation strength at the graft-bone interface, providing quicker graft-bone healing.

Tibial Rotation in Anterior Cruciate Ligament (ACL)-Deficient and ACL-Reconstructed Knees

Excessive tibial rotation has been documented in anterior cruciate ligament (ACL) deficiency during walking. ACL reconstruction has been unable to correct this abnormality in activities that are more demanding than walking and involve both anterior and rotational loading of the knee. These findings persist regardless of graft selection for the ACL reconstruction (bone-patellar tendon-bone or semitendinosus gracilis). Based on this research work, we propose a theoretical perspective for the development of osteoarthritis in both the ACL-deficient and the ACL-reconstructed knee. We propose that excessive tibial rotation will lead to abnormal loading of the cartilage areas that are not commonly loaded in the healthy knee. Over time, this abnormal loading will lead to osteoarthritis. We hypothesise that the development of new surgical procedures and grafts, such as a more horizontally oriented femoral tunnel or a double-bundle ACL reconstruction, could possibly restore tibial rotation to normal levels and prevent future knee pathology. However, in vivo gait analysis studies are needed to examine the effects of these surgical procedures on tibial rotation. Prospective in vivo and in vitro studies are also necessary to verify or refute our theoretical proposition for the development of osteoarthritis.

Intraarticular rupture pattern of the ACL

To date, the intraarticular rupture pattern of the anterior cruciate ligament (ACL) has not been reported. The ACL is a complex structure consisting of two functionally synergistic structures: the anteromedial (AM) and posterolateral (PL) bundle. The purpose of our study was to evaluate the intraarticular rupture pattern of the ACL with regard to its two functional bundles. We examined ACL rupture patterns with regard to the integrity of AM and PL bundle in 121 consecutive patients undergoing anterior cruciate ligament reconstruction surgery within 120 days after injury. The intraarticular pattern was observed by one experienced surgeon. In 25% of the patients a partial rupture of the ACL was found, whereas in the remaining 75% a complete rupture of AM and PL bundles was seen. A partial rupture could only be detected by careful dissection of the ligament. In 44% of all patients the AM and PL bundles did not rupture at the same location. In 12% of the patients the PL bundle showed no signs of rupture. When performing ACL reconstruction, care should be taken when dissecting down the ACL remnants to evaluate intact fiber bundles of the ACL.

A prospective study of 3-day versus 2-week immobilization period after anterior cruciate ligament reconstruction

BACKGROUND

Aggressive early rehabilitation is recommended after reconstruction of the anterior cruciate ligament (ACL) using a patellar tendon-bone graft. However, rehabilitation after reconstruction of ACL using the multistranded hamstring is controversial. In this study, we compared the clinical results of 3-day immobilization after reconstruction of ACL using the multistranded hamstring, with those of 2-week immobilization prospectively.

METHODS

A total of 30 consecutive patients with ruptured ACL underwent single-socket ACL reconstruction. 10 male and 5 female patients (mean age of 29.2+/-10.0 years) were prospectively randomized for a 3-day immobilization period, and 6 male and 9 female patients (mean age of 27.3+/-10.9 years) were randomized for a 2-week immobilization period. We measured the anterior laxity with a KT-2000 arthrometer, joint position sense, and thigh muscle strength at 3, 6 and 12 months after surgery.

RESULTS AND CONCLUSIONS

There were no statistically significant differences between the two groups. We concluded that the post-operative 3-day immobilization period is preferable to the longer 2-week period in our rehabilitation program from the viewpoint of psychological load to the patients and the duration of hospitalization after ACL reconstruction using multistranded hamstring tendons.

Anatomy of the anterior cruciate ligament with regard to its two bundles

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

Anterior cruciate ligament anatomy and function relating to anatomical reconstruction

Recently, the interest in surgical techniques that reconstruct the anteromedial (AM) and the posterolateral (PL) bundles of the anterior cruciate ligament (ACL) has risen. This review focuses on the structural as well as the mechanical properties of the ACL and the anatomical details of the femoral origin, midsubstance, and tibial insertion of AM and PL bundles of the ACL. The terminology of AM and PL bundles is chosen according to the tibial insertion and determined by their functional tensioning pattern throughout knee flexion. Close to extension the AM is moderately loose and the PL is tight. As the knee is flexed, the femoral attachment of the ACL becomes more horizontally oriented, causing the AM bundle to tighten and the PM bundle to loosen up. The ACL has been described to be restraint to anterior tibial displacement and internal tibial rotation. The rotational component might be represented by the PL bundle. The femoral origin has an oval shape with the center of the AM close to over-the-top position and the center of the PL close to the anterior and inferior cartilage margin. Tibial and femoral insertions of the ACL are over 3.5 times larger when compared to the midsubstance and tunnel placement is more challenging because of the limited size of potential grafts selection of tunnel site placement. For reconstruction, both bone-patellar tendon-bone (BPTB) and quadrupled hamstring grafts are used. Structural properties of a 10 mm wide BPTB or quadrupled hamstring graft have been reported to be comparable with those of the native ACL.

Reconstruction of the anterior cruciate ligament using bone-patellar tendon-bone graft with double biodegradable femoral pin fixation

The purpose of this study was to evaluate the early clinical outcomes of the bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstruction using biodegradable cross pin fixation. The nature of this study is a prospective nonrandomized clinical outcome study. Thirty-five patients who underwent BPTB ACL reconstruction with a minimum of 2 years follow-up evaluation were included in the study. Thirty BPTB autografts and five BPTB allografts were fixed with two biodegradable 2.7 mm cross pins (Rigid Fix) on the femoral side. Clinical evaluation included International Knee Documentation Committee (IKDC), Lysholm and Tegner activity score, and Telos stress device measurements. The average Lysholm knee score was 94.7 (of 100). Twenty-four patients reported an excellent result. The other eight patients were in a good group. According to the IKDC scores, 23 (66%) patients reported normal function, 12 (34%) patients reported nearly normal function, and no (0%) patient reported abnormal or severely abnormal function. Telos stress device values were less than 3 mm of sagittal displacement in 28 patients and 5 mm in 7 patients. No patients complained that their knees gave way fully, even with moderate or strenuous activities. All of the patients have returned to their preinjury level of activity and athletic participation. Clinical results support this technique as a reliable alternative for patellar tendon fixation in ACL reconstruction.

Effect of extraction protocols and epidermal growth factor on the cellular repopulation of decellularized anterior cruciate ligament allografts

We are developing a decellularized bone-anterior cruciate ligament (ACL)-bone allograft for treatment of ACL disruption in young or active patients. This study demonstrates the feasibility of seeding decellularized ACL tissue with primary ligament fibroblasts. Porcine ACLs were decellularized by one of three protocols, each differing only by the detergent/solvent used during the second wash (SDS, Triton-X, or TnBP). Porcine ACL fibroblasts were obtained by explant and seeded onto tissue samples of decellularized ACL. Culture conditions were varied to compare the relative effect of three different decellularization protocols on cellular repopulation. Culture condition variables included (1) the number of cells used for seeding, (2) the addition of epidermal growth factor (EGF), and (3) culture duration. Cellular ingrowth was assessed by metabolic activity (MTT assay), DNA quantification (Hoescht dye), and histology (H&E staining). Cell counting on histological sections demonstrated that Triton-X-and TnBP-treated ligaments were more receptive to cellular ingrowth than SDS-treated samples. The addition of EGF to culture medium did not significantly increase cellular ingrowth. Both the Triton-X and TnBP decellularization treatments provide suitable, naturally derived scaffolds for the ingrowth of primary ACL fibroblasts, and should be further investigated in the development of an allograft-derived bone-ACL-bone graft.

Arthroscopic single-stranded semitendinosus tendon- versus PDS-augmentation of reinserted acute femoral anterior cruciate ligament tears: 7 year follow-up study

This study reviews the long-term results of acute complete femoral tears or combined femoral (2/3 of the ligament diameter) /interstitial tears of the anterior cruciate ligament (ACL) that were reinserted. Out of 27 patients, 11 were treated with reinsertion plus augmentation with single-stranded semitendinosus tendon, 16 patients had a reinsertion and augmentation with a double-stranded PDS-band. Operation was carried out 10 (2-42) days after trauma. A brace was applied for 12 weeks, full weight bearing was allowed after 6 weeks according to our standard rehabilitation protocol. Twenty two patients (81%) could be reevaluated after a mean follow-up time of 7 years 1 month (range 3 years 8 months -11 years 5 months). No statistically significant difference was found between both techniques concerning patient's satisfaction and subjective evaluation of knee function, OAK-scores (semitendinosus-augmentation: 96 point, SD 2.0 PDS-augmentation: 94 points, SD 5.1) and IKDC-scores. Only in the PDS-augmentation group a statistically significant decrease was found in the level of activity in sports (P=0.046). At follow-up, radiological evaluation of the anterior drawer test was performed. In the group of patients who had undergone semitendinosus augmentation (n=9), anterior displacement of the tibia (determined radiologically using the TELOS-device) of 0-2 mm was found in five patients, displacement of 3-5 mm was seen in three cases and displacement of 6-10 mm in one patient (average 2.7 mm). Patients treated with PDS-augmentation (n=13) showed anterior tibial displacement of 0-2 mm in five cases, 3-5 mm in five cases, and 6-10 mm in two knees (average 3.6 mm). One patient of this group underwent ACL-reconstruction 6 years after reinsertion because of recurrent instability. At follow up, flexion was limited to less than 135 degrees in three patients (12.5%). One patient who had undergone semitendinosus augmentation and three patients from the PDS-augmentation group developed a cyclops syndrome and intraarticular adhesions that were treated arthroscopically 6 to 18 month after reinsertion surgery. A tendency towards a higher rate of limitation in range of motion was found for the PDS augmentation group. The reinsertion of a femoral torn ACL plus augmentation with a single strand of semitendinosus tendon or a PDS-band leads to acceptable results, an aggressive rehabilitation protocol may help to decrease the rate of limitation of flexion.

Comparison of initial mechanical properties of 4 hamstring graft femoral fixation systems using nonpermanent hardware for anterior cruciate ligament reconstruction: an in vitro animal study

PURPOSE

To compare the initial mechanical characteristics of 4 systems used to fix tendons to the femur during anterior cruciate ligament reconstruction.

METHODS

A total of 32 porcine femurs were used to study the following fixation systems: Bioabsorbable interference screw (Stryker, Kalamazoo, MI), Bio-Transfix Cross-pin (Arthrex, Naples, FL), Biosteon Cross-pin (Stryker), and a fixation technique based on wrapping the graft around the femoral condyle itself, thus allowing it to be fixed in place without the use of any hardware. The mechanical characteristics of each system were obtained by a preconditioned failure tensile test.

RESULTS

The yield load values (990.9 +/- 242.6 N for Bio-Transfix, 905.1 +/- 158.8 N for Biosteon Cross-pin, 684.4 +/- 119.7 N for the without-hardware system (WHS), and 369.4 +/- 120.1 N for the interference screw) revealed significant differences between the techniques that used cross-pins and the other 2 techniques (P < .006) on the one hand, and between the without hardware technique and the interference screw (P < .004) on the other. The stiffness of the 2 cross-pin fixation systems (117.6 +/- 22.5 N for Bio-Transfix and 112.6 +/- 22.5 N for Biosteon) was greater (P < .01) than those of the other systems (79.4 +/- 15.2 N for the WHS and 68.5 +/- 13 N for the interference screw).

CONCLUSIONS

The initial biomechanical properties of the 2 cross-pin fixation systems proved to be superior to those of the other 2 systems studied. The WHS fixation system exhibited better mechanical properties than its interference screw counterpart.

CLINICAL RELEVANCE

The better initial mechanical characteristics encountered using the Bio-Transfix and Biosteon Cross-pin systems indicate that these systems are better equipped to bear the loads generated by aggressive rehabilitation. The WHS fixation system provides an alternative to interference screw fixation.

Selection of cell source for ligament tissue engineering

Use of appropriate types of cells could potentially improve the functionality and structure of tissue engineered constructs, but little is known about the optimal cell source for ligament tissue engineering. The object of this study was to determine the optimal cell source for anterior cruciate ligament (ACL) tissue engineering. Fibroblasts isolated from anterior cruciate ligament, medial collateral ligament (MCL), as well as bone marrow mesenchymal stem cells (MSC) were compared using the following parameters: proliferation rate, collagen excretion, expression of collagen type I, II, and III, as well as alpha-smooth muscle actin. Green fluorescent protein (GFP) transfected MSCs were used to trace their fate in the knee joints. MSC, ACL, and MCL fibroblasts were all highly stained with antibodies for collagen types I and III and alpha-smooth muscle actin while negatively stained with collagen type II. Proliferation rate and collagen excretion of MSCs were higher than ACL and MCL fibroblasts (p < 0.05), and MSCs could survive for at least 6 weeks in knee joints. In summary, MSC is potentially a better cell source than ACL and MCL fibroblasts for anterior cruciate ligament tissue engineering.

Joint laxity and isokinetic thigh muscle strength characteristics after anterior cruciate ligament reconstruction: bone patellar tendon bone versus quadrupled hamstring autografts

OBJECTIVES

To analyze ligamentous stability and isokinetic strength of knee extensor and flexor muscles after anterior cruciate ligament reconstruction using 2 different autografts with identical fixation.

DESIGN

This study implements a comparative case series design.

SETTING

Schulthess Clinic, Switzerland.

PATIENTS

A total of 153 consecutive patients (n = 87 bone-patellar tendon-bone [BPTB]/66 quadruple semitendinosus/gracilis tendons [QSGT] patients) who underwent BPTB and QSGT surgery were functionally assessed.

INTERVENTION

All patients were functionally assessed (knee extension/flexion isokinetic strength and knee joint laxity) at a mean follow-up time of 11 months.

MAIN OUTCOME MEASUREMENTS

Laxity was measured utilizing the Kneelax arthrometer, whereas isokinetic strength of the knee extensor/flexor muscle groups was measured using the Biodex Multi Joint System 2 (180 degrees/s and 300 degrees/s).

RESULTS

The QSGT group had significantly greater knee joint laxity when compared with the BPTB group (P < 0.001). Furthermore, females in the QSGT group demonstrated the greatest knee joint laxity overall (P < 0.001). Additionally, a significant flexor torque deficiency was demonstrated in the QSGT group (P < 0.001); however, no differences in extensor torque were observed.

CONCLUSIONS

The use of a BPTB autograft achieved better knee joint stability as well as greater knee flexor torque than the QSGT autograft. Both grafts exhibited a similar knee extensor torque deficit, indicating that only quadriceps strength is not graft-dependent.

The fate of host and graft cells in early healing of bone tunnel after tendon graft

BACKGROUND

The behavior of host and graft cells during the healing process after autologous tendon graft has not been elucidated.

HYPOTHESIS

Host cells will integrate into the bone-tendon interface and contribute to cellular repopulation of the graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve-week-old, genetically identical, female green fluorescent protein transgenic rats (n = 20) and wild-type rats (n = 20) were used. The rats were divided into 2 experimental groups. In group A, the Achilles tendons of wild-type rats were harvested and transplanted into the transcondylar femoral bone tunnels of green fluorescent protein rats. In group B, the Achilles tendons of green fluorescent protein rats were transplanted into a transcondylar femoral bone tunnel of wild-type rats. Immediately after transplantation (time zero) and at 1, 2, and 4 weeks after the transplantation, distal femoral epiphyses were harvested and cut into 14-mum serial sagittal frozen sections. The sections were examined with a confocal laser-scanning microscope to quantify green fluorescent protein-positive cell survival.

RESULTS

At time zero, only host cells in group A and only graft cells in group B demonstrated green fluorescent protein signals. At 1 week in group A, many green fluorescent protein-positive cells were found in the graft. In group B, a few green fluorescent protein-positive cells were found in the graft. At 2 and 4 weeks in group A, many green fluorescent protein-positive cells were detected in the graft, but green fluorescent protein-positive cells had disappeared completely in group B.

CONCLUSION

Host cells, rather than graft cells, contribute to repair of the bone-tendon interface and the remodeling of grafts after simulated autologous tendon graft.

Effectiveness of three extraction techniques in the development of a decellularized bone–anterior cruciate ligament–bone graft

In this study, porcine bone-anterior cruciate ligament-bone (B-ACL-B) grafts were decellularized using one of three protocols incorporating surfactants lauryl sulfate (SDS), Triton X-100, and/or an organic solvent (tributyl phosphate (TnBP)). The effectiveness of Triton-SDS, Triton-Triton or Triton-TnBP treatments in removing cellular materials was determined and possible changes in biochemical composition and mechanical properties due to each treatment were investigated. Treatment with Triton-SDS was most effective at removing cell nuclei and intracellular protein (vimentin) from the ACL but affected both the collagen and glycosaminoglycan (GAG) components of the extracellular matrix while increasing the tensile stiffness of the ligament. Triton-Triton was the least effective of the three treatments in terms of cellular extraction, but did not significantly change the mechanical and biochemical properties of the ACL. Triton-TnBP matched the level of decellularization achieved by Triton-SDS in terms of visible cell nuclei; however, the extraction of intracellular vimentin was less consistent. TnBP treatment also slightly decreased the collagen content of the ACL but did not alter its mechanical properties. Overall, all three decellularization treatments maintained adequate mechanical and biochemical properties of B-ACL-B grafts to justify the further investigation of all three decellularization protocols. The selection of a superior treatment will depend on future studies of the propensity of treated tissues for repopulation by host ACL fibroblasts and, ultimately, on any immunogenic and/or remodeling host response induced in vivo.

[MRI after meniscus and cruciate ligament surgery]

Nowadays, due to its high diagnostic accuracy, MR imaging is the method of choice for the evaluation of knee joint disorders pre- and postoperatively. Accurate diagnosis is sometimes possible only if the reporting radiologist has knowledge of the therapeutic procedures and the surgical report. Frequently, further therapeutic management is strongly influenced by MR examinations and radiological reports.