The Use Of Hamstring Tendons For Anterior Cruciate Ligament Reconstruction

Investigating the effect of autograft diameter for quadriceps and patellar tendons use in anterior cruciate ligament reconstruction: a biomechanical analysis using a simulated Lachman test

Introduction

Current clinical practice suggests using patellar and quadriceps tendon autografts with a 10 mm diameter for ACL reconstruction. This can be problematic for patients with smaller body frames. Our study objective was to determine the minimum diameter required for these grafts. We hypothesize that given the strength and stiffness of these respective tissues, they can withstand a significant decrease in diameter before demonstrating mechanical strength unviable for recreating the knee's stability.

Methods

We created a finite element model of the human knee with boundary conditions characteristic of the Lachman test, a passive accessory movement test of the knee performed to identify the integrity of the anterior cruciate ligament (ACL). The Mechanical properties of the model's grafts were directly obtained from cadaveric testing and the literature. Our model estimated the forces required to displace the tibia from the femur with varying graft diameters.

Results

The 7 mm diameter patellar and quadriceps tendon grafts could withstand 55-60 N of force before induced tibial displacement. However, grafts of 5.34- and 3.76-mm diameters could only withstand upwards of 47 N and 40 N, respectively. Additionally, at a graft diameter of 3.76 mm, the patellar tendon experienced 234% greater stiffness than the quadriceps tendon, with similar excesses of stiffness demonstrated for the 5.34- and 7-mm diameter grafts.

Conclusions

The patellar tendon provided a stronger graft for knee reconstruction at all diameter sizes. Additionally, it experienced higher maximum stress, meaning it dissociates force better across the graft than the quadriceps tendon. Significantly lower amounts of force were required to displace the tibia for the patellar and quadriceps tendon grafts at 3.76- and 5.34-mm graft diameters. Based on this point, we conclude that grafts below the 7 mm diameter have a higher chance of failure regardless of graft selection.

Comparison of side-cutting maneuvers versus low impact baseball swing on knee ligament loading in adolescent populations

BACKGROUND

High impact sports are associated with an increased incidence rate for knee ligament injuries, specifically pertaining to the anterior cruciate ligament and medial collateral ligament. What is less clear is (i) the extent to which high impact activities preferentially load the anterior cruciate ligament versus the medial collateral ligament, and (ii) whether both ligaments experience similar stretch ratios during high loading scenarios. Therefore, the goal of this project was to assess how different loading conditions experienced through more at-risk sporting maneuvers influence the relative displacements of the anterior cruciate ligament and medial collateral ligament. The focus of the study was on adolescent patients - a group that has largely been overlooked when studying knee ligament biomechanics.

METHODS

Through kinetic knee data obtained through motion capture experimentation, two different loading conditions (high vs low impact) were applied to 22 specimen-specific adolescent finite element knee models to investigate the biomechanical impact various sporting maneuvers place on the knee ligaments.

FINDINGS

The high impact side cutting maneuver resulted in 102% and 47% increases in ligament displacement compared to the low impact baseball swing (p < 0.05) for both the anterior cruciate ligament and medial collateral ligament.

INTERPRETATION

Quantifying biomechanical risks that sporting activities place on adolescent subjects provides physicians with insight into knee ligament vulnerability. More specifically, knowing the risks that various sports place on ligaments helps guide the selection of sports for at-risk patients (especially those who have undergone knee ligament surgery).

Posterior Approach With Small Incision Is a Safe Alternative to Anterior Approach for Hamstring Autograft Harvest in Adolescents

Background

There are potential drawbacks and complications associated with using the anterior approach to harvest the hamstring tendon as an autograft source for anterior cruciate ligament (ACL) and medial patellofemoral ligament (MPFL) reconstruction. A posterior harvest technique has been described as an alternative to an anterior approach in skeletally mature patients. The 2 approaches have not been compared in adolescents.

Purpose

We sought to compare the incision size and harvested tendon length produced by anterior and posterior hamstring harvest techniques in an adolescent population.

Methods

After obtaining consent, we prospectively collected data on a consecutive series of 115 adolescents undergoing ACL or MPFL reconstruction, including the length of the incision and of the harvested hamstring tendon. Demographic information including age, sex, and body mass index (BMI) was collected at the time of surgery.

Results

The mean age at the time of surgery was 14.3 ± 1.8 years (range: 9-21 years), and 43% (N = 50) of participants were male. Of the 115 hamstring autografts, 26 were harvested anteriorly and 89 were harvested posteriorly. Neither mean semitendinosus length nor mean gracilis length was significantly different when harvested anteriorly versus posteriorly. The posterior harvest group had a mean incision length that was significantly smaller than that of the anterior harvest group. No iatrogenic nerve injuries or neurovascular complications were observed in either group.

Conclusion

A posterior incision for hamstring autograft harvest provided an alternative approach in adolescents, which resulted in a 20% smaller incision than an anterior approach. For procedures such as MPFL reconstruction that do not require concomitant anteromedial work, posterior hamstring harvest may be used to improve cosmesis while producing viable hamstring autograft tissue for surgical reconstruction.

Effects of and Response to Mechanical Loading on the Knee

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

A modified oblique incision in hamstring tendon graft harvesting during ACL reconstruction

BACKGROUND

During anterior cruciate ligament (ACL) reconstruction, different methods of harvesting hamstring tendon may lead to different degrees of injury to the inferior patellar branch of the saphenous nerve (IPBSN). Most of recent studies in the literature suggest that the classic oblique incision (COI) can reduce the incidence of IPBSN injury. We proposed a modified oblique incision (MOI) and compared it with the COI in terms of the resulting levels of injury and sensory loss and the clinical outcome.

METHODS

Patients with ACL injury admitted to our hospital from April 2015 to July 2019 were randomly selected and included in our study. Thirty patients underwent the COI to harvest hamstring tendons, and the other 32 patients underwent the MOI. The pin prick test was performed to detect the sensation loss at 2 weeks, 6 months, and 1 year after the operation. Digital photos of the region of hypoesthesia area were taken, and then, a computer software (Adobe Photoshop CS6, 13.0.1) was used to calculate the area of the hypoesthesia. The length of the incision and knee joint functional score were also recorded.

RESULTS

At the final follow-up, the incidence of IPBSN injury in COI and MOI were 33.3% and 9.4%, and the areas of paresthesia were 26.4±2.4 cm² and 9.8±3.4 cm² respectively. There was no significant difference in the incision length or knee functional score between the two groups.

CONCLUSION

The MOI can significantly reduce the risk of injury to the IPBSN, reduce the area of hypoesthesia, and lead to high subjective satisfaction. Therefore, compared with the COI, the MOI is a better method of harvesting hamstring tendons in ACL reconstruction.

The rule of twos: Technical note on consistent anatomical landmarks for hamstring graft harvesting

We describe a novel hamstring harvesting technique using the "Rule of Twos" as an aide-memoire to dissect the conjoint tendon in an Asian population undergoing anterior cruciate ligament reconstruction. In a prospective study performed on 17 patients to validate this technique, a 2cm incision is placed 2cm distal and medial to the tip of the tibial tubercle. The surgeon then measured the following variables and calculated their means: 1) Distance from the tip of the tibial tuberosity to the proximal edge of the conjoint tendon (19.4 ± 1.4mm), 2) Width of the conjoint tendon insertion (18.8 ± 1.0mm), 3) Conjoint tendon length (20.1 ± 1.0mm).

The effect of melt electrospun writing fiber orientation onto cellular organization and mechanical properties for application in Anterior Cruciate Ligament tissue engineering

The effect of melt electrospun writing fiber arrangement on cellular behavior has not yet been thoroughly investigated. Cellular orientation is particularly important in the context of ligament tissue engineering for orthopedic applications whereby a high degree of cell alignment is present in the native tissue. The aim of this study was to investigate the response of human mesenchymal stem cells (hMSC) to three different patterned porous polycaprolactone scaffolds (aligned, crimped and random) fabricated by melt electrospinning writing, resulting in 20 μm diameter electrospun fibers. Cell orientation was investigated over 4 weeks in vitro and it was demonstrated that the aligned pattern was capable of orientating the hMSCs towards the main direction of the fibers and this feature was maintained over the entire culture period whereas the orientation was rapidly lost in the crimped pattern. In order to fabricate a functional scaffold for ligament tissue engineering, the scaffolds were rolled in three bundles, subsequently braided and combined with a bone compartment (consisting of a melt electrospun scaffold seeded with osteogenically induced hMSCs) for the development of a Bone-Ligament-Bone (BLB) construct. The mechanical properties of non-cellularized and cellularized BLB constructs were assessed under both quasi-static and cyclic conditions. This revealed that the in vitro maturation significantly softened the BLB constructs and that the mechanical properties were several fold lower than those of native tissue. The cyclic testing demonstrated that the presence of cell sheets resulted in increased resilience and elasticity, even though the global mechanical properties were decreased for the in vitro matured constructs (regardless of the pattern). In conclusion, we demonstrated that melt electrospinning writing fiber organization can induce spontaneous cell alignment and that large cellularized BLB constructs with complex geometry can achieve mechanical resilience under cyclic stretching.

Effectiveness of Reconstruction of the Anterior Cruciate Ligament with Quadrupled Hamstrings and Bone-Patellar Tendon-Bone Autografts

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.

Oblique incisions in hamstring tendon harvesting reduce iatrogenic injuries to the infrapatellar branch of the saphenous nerve

PURPOSE

Iatrogenic injury to the infrapatellar branch of the saphenous nerve (IPBSN) is associated with many surgical interventions to the medial aspect of the knee, such as anterior cruciate ligament (ACL) reconstruction. Different types of surgical incisions during hamstring tendon harvesting for ACL reconstruction are related to a variable risk of IPBSN injury. This study aimed to evaluate the risk of iatrogenic IPBSN injury during hamstring tendon harvesting for ACL reconstruction with different incision techniques over the pes anserinus.

METHODS

This study was performed on 100 cadavers. Vertical, horizontal, or oblique incisions were simulated on each cadaveric limb to determine the incidence of iatrogenic IPBSN injury.

RESULTS

The vertical incision caused the IPBSN injury during hamstring tendon harvesting in 101 (64.7%), the horizontal incision in 78 (50.0%), and the oblique incision in 43 (27.6%) examined lower limbs. The calculated odds ratios (OR) for risk of injury in vertical versus horizontal and horizontal versus oblique incisions were 2.4 (95% CI 1.5-3.6) and 1.8 (95% 1.2-2.8), respectively.

CONCLUSIONS

The vertical incision technique over the pes anserinus should be avoided during hamstring tendon harvesting for ACL reconstruction. The adoption of an oblique incision, with the shortest possible length, will allow for the safest procedure possible, thus minimizing the risk of iatrogenic IPBSN injury, and improving patient outcomes and postoperative quality-of-life.

Multiple extensor tendons reconstruction with hamstring tendon grafts and flap coverage for severe dorsal hand injuries

Treatment of patients with traumatic loss of skin and multiple extensor tendons on the dorsum of the hand is a challenge. The aim of this study was to assess the outcome after reconstruction of soft tissues and multiple extensor tendons in patients who suffered traumatic loss of skin and multiple extensor tendons. Ten patients were enrolled in the study. These patients underwent single-stage reconstruction with autogenous hamstring tendon grafts for multiple extensor tendon defects and fasciocutaneous flaps for coverage of dorsal hand defects. In total, 25 tendons (2 tendons in 5 patients and 3 tendons in 5 patients) were reconstructed. The semitendinosus tendon was used in all patients and the gracilis tendon was added in five patients for tendon reconstruction. Total tendon length requiring reconstruction was between 9cm and 31cm. Free anterolateral thigh flaps were used in six patients and reverse pedicled forearm flaps were used in four patients. According to Miller's scoring system, 8 fingers had excellent results, 12 fingers had good results and 5 fingers had fair results at the final follow-up. Hamstring tendons can be used satisfactorily for primary reconstruction of multiple digital extensor tendons due to their availability and compatibility, with a fasciocutaneous flap.

LEVEL OF EVIDENCE

IV.

Muscle contributions to medial tibiofemoral compartment contact loading following ACL reconstruction using semitendinosus and gracilis tendon grafts

Background

The muscle-tendon properties of the semitendinosus (ST) and gracilis (GR) are substantially altered following tendon harvest for the purpose of anterior cruciate ligament reconstruction (ACLR). This study adopted a musculoskeletal modelling approach to determine how the changes to the ST and GR muscle-tendon properties alter their contribution to medial compartment contact loading within the tibiofemoral joint in post ACLR patients, and the extent to which other muscles compensate under the same external loading conditions during walking, running and sidestep cutting.

Materials and methods

Motion capture and electromyography (EMG) data from 16 lower extremity muscles were acquired during walking, running and cutting in 25 participants that had undergone an ACLR using a quadruple (ST+GR) hamstring auto-graft. An EMG-driven musculoskeletal model was used to estimate the medial compartment contact loads during the stance phase of each gait task. An adjusted model was then created by altering muscle-tendon properties for the ST and GR to reflect their reported changes following ACLR. Parameters for the other muscles in the model were calibrated to match the experimental joint moments.

Results

The medial compartment contact loads for the standard and adjusted models were similar. The combined contributions of ST and GR to medial compartment contact load in the adjusted model were reduced by 26%, 17% and 17% during walking, running and cutting, respectively. These deficits were balanced by increases in the contribution made by the semimembranosus muscle of 33% and 22% during running and cutting, respectively.

Conclusion

Alterations to the ST and GR muscle-tendon properties in ACLR patients resulted in reduced contribution to medial compartment contact loads during gait tasks, for which the semimembranosus muscle can compensate.

Combining electrospinning and cell sheet technology for the development of a multiscale tissue engineered ligament construct (TELC)

Ligament tissue rupture is a common sport injury. Although current treatment modalities can achieve appropriate reconstruction of the damaged ligament, they present significant drawbacks, mostly related to reduced tissue availability and pain associated with tissue harvesting. Stem cell based tissue regeneration combined with electrospun scaffolds represents a novel treatment method for torn ligaments. In this study, a low fiber density polycaprolactone (PCL) electrospun mesh and sheep mesenchymal stem cells (sMSCs) were used to develop tissue engineered ligament construct (TELC) in vitro. The assembly of the TELC was based on the spontaneous capacity of the cells to organize themselves into a cell sheet once seeded onto the electrospun mesh. The cell sheet matured over 4 weeks and strongly integrated with the low fiber density electrospun mesh which was subsequently processed into a ligament-like bundle and braided with two other bundles to develop the final construct. Live/dead assay revealed that the handling of the construct through the various phases of assembly did not cause significant difference in viability compared to the control. Mechanical evaluation demonstrated that the incorporation of the cell sheet into the braided construct resulted in significantly modifying the mechanical behavior. A stress/displacement J-curve was observed for the TELC that was similar to native ligament, whereas this particular feature was not observed in the non-cellularized specimens. The regenerative potential of the TELC was evaluated ectopically in immunocompromized rats, compared to non cellularized electrospun fiber mesh and this demonstrated that the TELC was well colonized by host cells and that a significant remodelling of the implanted construct was observed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 399-409, 2018.

Injury of the infrapatellar branch of the saphenous nerve due to hamstring graft harvest

PURPOSE

Sensory disturbance around the surgical incision due to injury of the infrapatellar branch of the saphenous nerve can be seen in the anterior cruciate ligament reconstruction. In this research, we aimed to compare the incidence, extent of sensory loss, its clinical effect, and natural course caused by two different skin incisions used for hamstring graft harvest.

METHODS

Vertical incision for 36 patients and oblique incision for 42 patients used for graft harvest were included in this study. Sensory loss areas were documented at 6th week, 3rd month and 6th month. Pin prick examination is used to detect the change in sensation. Digital photographs of hypaesthesia were taken and analysed by computer for area detection. The length of incision and subjective complain of sensory loss were also noted.

RESULTS

At 6th month, 77% (28/36) of the vertical incisions were associated with persistent sensory loss when compared to the oblique incision (45%, 19/42). The measured area of hypaesthesia was significantly higher in vertical incision (42.4 ± 22.3 cm²) than that in oblique incision (9.3 ± 15.3 cm²) at 6th month. The area of hypaesthesia gradually shrunk in size from distal to proximal in direction. Also, subjective cutaneous anaesthesia was higher in vertical incision (15/36, 41%) than oblique incision (6/41, 14%) at 6th month.

CONCLUSION

Oblique incision with less risk of nerve damage is better for graft harvesting. Area of hypaesthesia gradually reduces with time and even recover totally. As a possible complication, nerve injury and its benign prognosis should be explained to the patient before surgery.

Morphologic Characteristics and Strength of the Hamstring Muscles Remain Altered at 2 Years After Use of a Hamstring Tendon Graft in Anterior Cruciate Ligament Reconstruction

BACKGROUND

The hamstring tendon graft used in anterior cruciate ligament (ACL) reconstruction has been shown to lead to changes to the semitendinosus and gracilis musculature.

HYPOTHESIS

We hypothesized that (1) loss of donor muscle size would significantly correlate with knee muscle strength deficits, (2) loss of donor muscle size would be greater for muscles that do not experience tendon regeneration, and (3) morphological adaptations would also be evident in nondonor knee muscles.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Twenty participants (14 men and 6 women, mean age 29 ± 7 years, mean body mass 82 ± 15 kg) who had undergone an ACL reconstruction with a hamstring tendon graft at least 2 years previously underwent bilateral magnetic resonance imaging and subsequent strength testing. Muscle and tendon volumes, peak cross-sectional areas (CSAs), and lengths were determined for 12 muscles and 6 functional muscle groups of the surgical and contralateral limbs. Peak isokinetic concentric strength was measured in knee flexion/extension and internal/external tibial rotation.

RESULTS

Only 35% of the patients showed regeneration of both the semitendinosus and gracilis tendons. The regenerated tendons were longer with larger volume and CSA compared with the contralateral side. Deficits in semitendinosus and gracilis muscle size were greater for muscles in which tendons did not regenerate. In addition, combined hamstring muscles (semitendinosus, semimembranosus, and biceps femoris) and combined medial knee muscles (semitendinosus, semimembranosus, gracilis, vastus medialis, medial gastrocnemius, and sartorius) on the surgical side were reduced in volume by 12% and 10%, respectively. A 7% larger volume was observed in the surgical limb for the biceps femoris muscle and corresponded with a lower internal/external tibial rotation strength ratio. The difference in volume, peak CSA, and length of the semitendinosus and gracilis correlated significantly with the deficit in knee flexion strength, with Pearson correlations of 0.51, 0.57, and 0.61, respectively.

CONCLUSION

The muscle-tendon properties of the semitendinosus and gracilis are substantially altered after harvesting, and these alterations may contribute to knee flexor weakness in the surgical limb. These deficits are more pronounced in knees with tendons that do not regenerate and are only partially offset by compensatory hypertrophy of other hamstring muscles.

Arthroscopic single-bundle anterior cruciate ligament reconstruction with six-strand hamstring tendon allograft versus bone-patellar tendon-bone allograft

PURPOSE

The aim of this study was to compare the clinical outcomes of arthroscopic single-bundle anterior cruciate ligament (ACL) reconstruction with six-strand hamstring tendon (HT) allograft versus bone-patellar tendon-bone (BPTB) allograft.

METHODS

The prospective randomized controlled trial was included 129 patients. Sixty-nine patients received reconstruction with six-strand HT allografts (HT group), whereas 60 patients with BPTB allografts (BPTB group). Outcome assessment included re-rupture findings, International Knee Documentation Committee (IKDC) scores, Lysholm scores, KT-1000 arthrometer, Lachman test, pivot-shift test, range of motion (ROM) and single-leg hop test.

RESULTS

At a mean follow-up of 52 months, 113 patients (HT group, 61 patients; BPTB group, 52 patients) completed a minimum 4-year follow-up. Four patients in HT group and six in BPTB group experienced ACL re-rupture (6.2 vs. 10.3 %) and received revision surgery. Significant between-group differences were observed in KT-1000 outcomes and pivot-shift test 1 (1.2 ± 1.5 vs. 1.8 ± 1.3, p = 0.025; positive rate 6.5 vs. 18.9 %, p = 0.036), 2 (1.1 ± 1.4 vs. 1.6 ± 1.2, p = 0.044; 8.1 vs. 20.7 %, p = 0.039), 4 (1.1 ± 1.5 vs. 1.7 ± 1.4, p = 0.031; 9.7 vs. 25 %, p = 0.012) years postoperatively. The outcomes between the two groups were comparable in terms of IKDC scores, Lysholm scores, Lachman test, ROM and single-leg hop test.

CONCLUSIONS

Six-strand HT allograft achieved superior anteroposterior and rotational stability after single-bundle ACL reconstruction. It is a reasonable graft substitute for ACL reconstruction.

LEVEL OF EVIDENCE

II.

Arthroscopic Anterior Cruciate Ligament Reconstruction Using a Hamstring Graft with Interference Screw Fixation

Background and Aims:

This study assessed the clinical and radiographic results 3 to 8 years after an arthroscopic ACL reconstruction using a hamstring graft with interference screw fxation on femoral and tibial sites.

Material and Methods:

Seventy-six of 100 patients, who underwent an arthroscopic ACL reconstruction, could be re-examined with a mean follow-up of 5 years.

Results:

The mean Tegner activity score was 4 (scale: 0 to 10) before surgery, and 5 at the follow-up. Fifty-four patients (78%) achieved a satisfactory result in the IKDC rating. The mean Lysholm score was 85 (scale: 0 to 100), the score being better in patients without meniscal resection than those with (P = 0.04). The mean side-to-side difference in anterior-posterior knee laxity was 1.8 mm, and 62 patients (90%) had good stability. Sixty-four patients (93%) had normal range of motion of the knee. Twelve patients (46 %) with meniscal resection had osteoarthritic changes, compared with only 8 of those (20 %) without meniscal resection (P = 0.03).

Conclusions:

This medium-term follow-up study showed that good stability and function and normal range of motion of the knee can be achieved in majority of the patients who have undergone an ACL reconstruction with a hamstring graft and interference screw fixation.

Minimally invasive semitendinosus tendon harvesting from the popliteal fossa versus conventional hamstring tendon harvesting for ACL reconstruction: A prospective, randomised controlled trial in 100 patients

BACKGROUND

This study aims to compare a technique for hamstring tendon harvesting from a postero-medial incision in the popliteal fossa with the conventional method.

METHODS

One hundred patients who underwent anterior cruciate ligament (ACL)-reconstruction were randomised to either have their tendon graft harvested from postero-medial (group 1) or via an antero-medial approach (group 2). Time for tendon harvest, length of skin incision and duration of tendon harvest were recorded as well as complications and sensory disturbances in the lower leg. Pain scores were documented on the VAS scale.

RESULTS

Time for tendon harvesting averaged one minute 23 s in group 1 versus five minutes 20 s in group 2 (p<0.01). The skin incision measured 21 mm (group 1) versus 49 mm in group 2 (p<0.01). The length of the harvested tendon averaged 272 mm (group 1) and 292 mm in group 2 (p<0.01). There was one superficial wound infection in group 2 and none in group 1. Postoperative pain scores were similar in both groups. None of the patients in group 1 reported sensory disturbance in the lower leg, whilst seven patients in group 2 were found to have reduced sensation in the distribution of the saphenous nerve postoperatively (p<0.01).

CONCLUSION

This study confirms that harvesting the semitendinosus tendon from postero-medial is quicker, results in a shorter scar and reduces the risk of injury to branches of the saphenous nerve. However, harvesting the tendon from postero-medial resulted in a shorter tendon graft.

LEVEL OF EVIDENCE

Level I (Randomised, controlled trial).

Hamstring Tendon Regeneration After Harvest for Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To assess whether the portions of the semitendinosus and gracilis tendons harvested for anterior cruciate ligament reconstruction have the potential to regenerate and, if so, to evaluate the histologic properties and actual function of this newly formed tissue.

METHODS

We performed a comprehensive search of CINAHL (Cumulative Index to Nursing and Allied Health Literature), Embase, Medline, the Cochrane Central Registry of Controlled Trials, and SPORTDiscus from inception of the databases to July 2014, using various combinations of keywords. Studies focusing on hamstring tendon and muscle regeneration through imaging and histology, as well as on the related functional outcomes, were selected. We included studies assessing evidence of tissue regeneration with imaging (magnetic resonance imaging, 3-dimensional computed tomography, ultrasonography) or with histologic examination of biopsy samples (or a combination thereof).

RESULTS

Nineteen articles were included in this review, with a total of 400 patients observed. The overall rate of tissue regeneration was 86.0%, with similar values shown in most studies regardless of the methodology of the assessment. Biopsy confirmed that the tissue found at the site in 74% of the cases showed typical histologic features of the tendon. The mean modified Coleman Methodology Score of the studies included was 52.7 points, showing a modest methodologic quality for the studies published to date.

CONCLUSIONS

In over 85% of the cases analyzed, regeneration signs of the harvested tendon were found through different imaging and histologic methodologies. A torque deficit in deep knee flexion is always present postoperatively, but the cause for this is still unclear. There is a need for better-designed trials featuring a higher level of evidence to further investigate this matter, and the effects of postoperative care and the surgical approach used on the regeneration process should be analyzed in the future.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II, III, and IV studies.

Impact of Hamstring Graft Diameter on Tendon Strength: A Biomechanical Study

PURPOSE

The purpose of this study was to compare the tensile strength of hamstring grafts of varying combined pull-through diameters within the clinically relevant range of 6 to 9 mm.

METHODS

We tested 44 non-irradiated allograft hamstring grafts (11 per group). Combined looped semitendinosus and gracilis grafts were allocated to the 6-, 7-, 8-, or 9-mm group based on the smallest-diameter lumen that the graft could be "pulled through" using a surgical sizing instrument. Testing was performed on an Instron materials testing machine (Instron, Norwood, MA). Samples were secured with cryoclamps, prestressed, and pulled to failure at a rate of 10% gauge length per second.

RESULTS

The mean load to failure was 2,359 ± 474 N, 3,263 ± 677 N, 3,908 ± 556 N, and 4,360 ± 606 N for the 6-, 7-, 8-, and 9-mm grafts, respectively. Minimum failure loads were as low as 1,567 N, 2,288 N, 2,874 N, and 3,720 N for each group, respectively. There were statistically significant differences between the 6- and 7-mm, 6- and 8-mm, 6- and 9-mm, and 7- and 9-mm groups (P = .01).

CONCLUSIONS

Statistically different increasing tensile strength was seen as graft diameter increased. Significant variability exists in the strength of multi-stranded hamstring allografts within the diameter range of 6 to 9 mm that often falls well below the commonly accepted value of 4,000 N for a hamstring graft.

CLINICAL RELEVANCE

Recent evidence suggests a higher early failure rate of hamstring autografts in subsets of patients with graft diameters of 8 mm or less. This study may increase awareness that hamstring grafts may not be nearly as strong as previously appreciated and that increasing tendon diameters by 1 to 2 mm may dramatically affect graft strength. These data may be helpful in preoperative discussions regarding variable hamstring size, strength, and potential intraoperative augmentation options.

Nerve injury during hamstring graft harvest: a prospective comparative study of three different incisions

PURPOSE

To compare the incidence, extent of sensory loss, its clinical effect and natural course caused by three different skin incisions used for autogenous hamstring graft harvest during anterior cruciate ligament (ACL) reconstruction.

METHODS

One hundred and twenty patients who underwent hamstring graft harvest during ACL reconstruction, participated in the study. All patients were randomized into 3 groups as per the 3 incisions used-vertical, transverse and oblique. The area of sensory loss was documented as per anatomical distribution of the infrapatellar branch of saphenous nerve (IPSBN) and sartorial branch of sensory nerve (SBSN) at 6 weeks, 3 months and 6 months follow-ups. The length of incision, area of sensory loss and subjective pain score (out of 10) were also noted.

RESULTS

The incidence, area of hypesthesia and persistence at 6 months were significantly higher with vertical incision at all times, whereas it was the least with oblique incision. Injury to IPSBN was maximum with vertical incision (p = 0.000), and it was similar in the transverse and oblique incision groups. The SBSN injury incidence was not significantly different between the three groups (n.s.). Subjective cutaneous hypesthesia incidence was quite low in all the three groups. The oblique incision group had highest subjective satisfaction closely followed by the horizontal incision group.

CONCLUSIONS

Vertical incision has highest incidence of IPBSN injury, persistent hypesthesia, largest area of sensory loss and poorest subjective outcome. Oblique and transverse incision groups had statistically comparable results, though better outcome was noted in the oblique incision group. The SBSN injury was equally common in all the three incisions used. However, the sensory loss does not impair normal daily activities in the patients. We recommend use of oblique incision for hamstring graft harvest.

LEVEL OF EVIDENCE

Therapeutic randomized controlled prospective study, level I.

Revision ACL reconstruction using contralateral hamstrings

PURPOSE

Due to the increasing number of primary anterior cruciate ligament (ACL) reconstructions, the need for revision surgery has risen. The aim of this study was to evaluate the use of contralateral doubled semitendinosus and gracilis tendon (DGST) for revision anterior cruciate ligament reconstruction.

METHODS

Twelve patients undergoing revision ACL reconstruction with hamstring tendon were examined at an average follow-up of 3 years. All patients underwent a thorough subjective and objective evaluation, which included a KT-1000 arthrometric evaluation, and a radiographic examination.

RESULTS

Subjective evaluation yielded a median score of 5.5 (range 2-9) on the Tegner activity scale. The mean Lysholm score was 95 (SD 9.5), and the mean subjective IKDC 2000 score was 95.4 (SD 7.8). At physical examination, a negative Lachman test was found in ten patients; one patient had a positive Lachman test with a firm end-point, and one other patient had a clearly positive Lachman test. Two patients had a grade 1+ on pivot shift testing. Only 1 patient showed a side-to-side difference more than 5 mm at the maximum manual KT-1000 arthrometer. Three patients (25 %) showed initial signs of osteoarthritis.

CONCLUSIONS

The results of the study show that the use of hamstring tendons harvested from the unaffected knee represents a valid option for revision surgery following a failed primary ACL reconstruction using DGST grafts.

LEVEL OF EVIDENCE

IV.

Cruciate ligament loading during common knee rehabilitation exercises

Cruciate ligament injuries are common and may lead to dysfunction if not rehabilitated. Understanding how to progress anterior cruciate ligament and posterior cruciate ligament loading, early after injury or reconstruction, helps clinicians prescribe rehabilitation exercises in a safe manner to enhance recovery. Commonly prescribed therapeutic exercises include both weight-bearing exercise and non-weight-bearing exercise. This review was written to summarize and provide an update on the available literature on cruciate ligament loading during commonly used therapeutic exercises. In general, weight-bearing exercise produces smaller loads on the anterior cruciate ligament and posterior cruciate ligament compared with non-weight-bearing exercise. The anterior cruciate ligament is loaded less at higher knee angles (i.e. 50-100 degrees). Squatting and lunging with a more forward trunk tilt and moving the resistance pad proximally on the leg during the seated knee extension unloads the anterior cruciate ligament. The posterior cruciate ligament is less loaded at lower knee angles (i.e. 0-50 degrees), and may be progressed from level ground walking to a one-leg squat, lunges, wall squat, leg press, and the two-leg squat (from smallest to greatest). Exercise type and technique variation affect cruciate ligament loading, such that the clinician may prescribe therapeutic exercises to progress ligament loading safely, while ensuring optimal recovery of the musculoskeletal system.

Biomechanical properties of porcine flexor tendon fixation with varying throws and stitch methods

BACKGROUND

The well-known suture technique configurations used for hamstring tendon autograft preparation in anterior cruciate ligament (ACL) reconstruction are the Krackow locking stitch and nonlocking stitch, such as a baseball stitch and a whipstitch. However, there are few data in the literature regarding biomechanical comparisons of suture techniques.

PURPOSE

The purpose of this study was to determine the properties of several current techniques of tendon graft suture employed in ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-two fresh-frozen porcine flexor digitorum tendons were used. Three stitch configurations (Krackow stitch [group K], baseball stitch [group B], and whipstitch [group W]) were assessed with varying suture throws (6 throws, group×6; 10 throws, group×10) using No. 5 Ethibond sutures. Each group was tested at 1500 loading cycles between 50 and 200 N. After loading cycles, the surviving tendons underwent a load-to-failure test.

RESULTS

During the loading cycles, 3 of 7 specimens in group B×6 and all specimens in group W×6 failed by suture pullout. Four of 7 specimens in group B×10 and all specimens in group W×10 showed partial tearing of the tendon. Elongation of group B×10 and group W×10 showed significantly greater elongation than other groups (P < .05). Maximum loads at failure showed significant differences between group K and the other groups (K×6, 436 ± 52 N; K×10, 419 ± 34 N; P < .05). Most specimens failed by rupture of the suture thread in group K. Pullout of the suture from the tendon was observed most in groups B and W.

CONCLUSION

The Krackow stitch was superior to other stitch methods. There was, however, no significant effect of the number of throws on the holding strength.

CLINICAL RELEVANCE

The Krackow stitch could prevent suture slippage by a locking mechanism. The whipstitch is not suitable for clinical application even with an increased number of throws.

[Implant-free tibial fixations of the posterior cruciate ligament. Development and biomechanical testing]

BACKGROUND

A secure tibial press fit technique in posterior cruciate ligament reconstructions may be a relevant alternative to common techniques because no hardware is necessary. Up to the present point in time no biomechanical data exist for a tibial press fit posterior cruciate ligament (PCL) reconstruction. This study compares the biomechanical properties of hamstring and quadriceps tendon grafts using a press fit technique with those of an interference screw fixation.

METHODS

Quadriceps and hamstring tendons of 20 human cadavers (age 49.2±18.5 years) were used. A press fit fixation with a knot in the semitendinosus tendon (K) and a quadriceps tendon bone block graft (Q) were compared to an interference screw fixation (I) in 27 porcine tibiae. In each group, nine constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclical loading were investigated.

RESULTS

The maximum load to failure was 518±157 N (387-650 N) for the K group, 558±119 N (466-650 N) for the I group and 620±102 N (541-699 N) for the Q group. The stiffness was 55±27 N/mm (18-89 N/mm) for the K group, 117±62 N/mm (69-165 N/mm) for the I group and 65±21 N/mm (49-82 N/mm) for the Q group. The stiffness of the I group was significantly larger (ANOVA on ranks, P=0.01). The elongation during cyclical loading was significantly larger for all groups from the 1st to the 5th cycle compared to the elongation in between the 5th and the 20th cycle (P<0.03).

CONCLUSION

All techniques exhibited larger elongation during initial loading. Load to failure and stiffness were significantly different between the fixations. The Q fixation showed equal biomechanical properties compared to a pure tendon fixation (I) with an interference screw. The results of group K were inferior. All three investigated fixation techniques exhibit comparable biomechanical properties. Preconditioning of the constructs is critical. Future randomized, clinical trials have to investigate the biological effectiveness of these fixation techniques.

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.

The biomechanical and clinical application of using the anterior half of the peroneus longus tendon as an autograft source

BACKGROUND

The shortage of autogenous grafts has often times been a problem in knee ligament reconstruction. There are little data concerning the use of the anterior half of the peroneus longus tendon (AHPLT) as an autograft.

HYPOTHESIS

The AHPLT is a suitable graft with respect to its strength, safety, and donor site morbidity.

STUDY DESIGN

Descriptive laboratory study and case series; Level of evidence, 4.

METHODS

The safety and efficacy of using the AHPLT as an autograft source were evaluated. A cadaveric study was first done to reveal the anatomic profile of the AHPLT, to test its failure load, and to compare it with that of the semitendinosus and gracilis tendons. Then, a cadaveric harvest study was performed to show it was safe and reproducible. The space between the tendon stripper and the peroneal nerve during harvesting of the AHPLT was evaluated. Lastly, a clinical study was performed to evaluate donor site morbidity. The preoperative and postoperative foot and ankle functions of 92 patients who underwent a variety of knee ligament reconstructions with the AHPLT were followed for more than 2 years and were then evaluated using the American Orthopedic Foot and Ankle Society (AOFAS) scale and the Foot and Ankle Disability Index (FADI) to determine the influence of tendon removal on ankle and foot function.

RESULTS

The average failure load of the AHPLT was 322.35 ± 63.18 N, accounting for 97.69% ± 19.48% and 147.94% ± 41.30% of the semitendinosus and gracilis tendons, respectively. During tendon harvesting, the distance between the head of the tendon stripper and the branching point of the deep peroneus nerve was 4.6 to 10.4 cm. The clinical study showed that the preoperative and postoperative AOFAS scores were 97.4 ± 2.0 and 97.2 ± 1.6 (P = .85), respectively, while the FADI scores preoperatively and postoperatively were 96.8 ± 2.2 and 96.9 ± 2.5 (P = .91), respectively. No signs of peroneus nerve injury, peroneus longus tendon rupture, or tendinopathy were found.

CONCLUSION

The AHPLT is acceptable for use as an autograft with respect to its strength, safety, and donor site morbidity.

The fixation strength of tibial PCL press-fit reconstructions

PURPOSE

A secure tibial press-fit technique in posterior cruciate ligament reconstructions is an interesting technique because no hardware is necessary. For anterior cruciate ligament (ACL) reconstruction, a few press-fit procedures have been published. Up to the present point, no biomechanical data exist for a tibial press-fit posterior cruciate ligament (PCL) reconstruction. The purpose of this study was to characterize a press-fit procedure for PCL reconstruction that is biomechanically equivalent to an interference screw fixation.

METHODS

Quadriceps and hamstring tendons of 20 human cadavers (age: 49.2 ± 18.5 years) were used. A press-fit fixation with a knot in the semitendinosus tendon (K) and a quadriceps tendon bone block graft (Q) were compared to an interference screw fixation (I) in 30 porcine femora. In each group, nine constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness, and elongation during failure testing and cyclical loading were investigated.

RESULTS

The maximum load to failure was 518 ± 157 N (387-650 N) for the (K) group, 558 ± 119 N (466-650 N) for the (I) group, and 620 ± 102 N (541-699 N) for the (Q) group. The stiffness was 55 ± 27 N/mm (18-89 N/mm) for the (K) group, 117 ± 62 N/mm (69-165 N/mm) for the (I) group, and 65 ± 21 N/mm (49-82 N/mm) for the (Q) group. The stiffness of the (I) group was significantly larger (P = 0.01). The elongation during cyclical loading was significantly larger for all groups from the 1st to the 5th cycle compared to the elongation in between the 5th to the 20th cycle (P < 0.03).

CONCLUSION

All techniques exhibited larger elongation during initial loading. Load to failure and stiffness was significantly different between the fixations. The Q fixation showed equal biomechanical properties compared to a pure tendon fixation (I) with an interference screw. All three fixation techniques that were investigated exhibit comparable biomechanical properties. Preconditioning of the constructs is critical. Clinical trials have to investigate the biological effectiveness of these fixation techniques.

Morphology of hamstring torque-time curves following ACL injury and reconstruction: mechanisms and implications

The purposes of this study were (i) to examine the effects of anterior cruciate ligament (ACL) status on hamstring force steadiness, peak hamstring strength, quadriceps (antagonist) activation, and physical performance, and (ii) to evaluate the associations of physical performance with hamstring steadiness and hamstring strength. Thirteen subjects with unilateral deficiency of the ACL (ACLD), 39 matched subjects with unilateral reconstructed ACL (ACLR; n = 25 with bone-patella tendon-bone (ACLR-PT) graft and n = 14 with combined semitendinosus and gracilis tendon (ACLR-STGT) graft) and 33 control subjects participated. Each subject performed maximal-effort isokinetic knee flexion repetitions at 180° s(-1) with electromyography (EMG) electrodes attached to their medial and lateral quadriceps muscles. Physical performance was assessed using the single-limb long hop for distance. Wavelet-derived mean instantaneous frequency (Mif) of flexor torque-time curves was significantly (p < 0.05) higher (i.e., less smooth) in ACLR-STGT subjects compared to the ACLD, ACLR-PT and control subjects. No significant differences existed for peak hamstrings strength (i.e., peak torque produced) or quadriceps antagonist EMG activity. Positive correlations were identified between hamstrings force steadiness and quadriceps antagonist activity for ACLD (r =  0.797), ACLR-PT (r = 0.467), and ACLR-STGT (r = 0.628) subjects. For ACLR-STGT subjects, reduced hamstrings force steadiness associated with poorer long-hop performance (r = -0.695). Reduced steadiness amongst ACLR-STGT subjects may reflect motor output variability of the antagonist (i.e., quadriceps dyskinesia) and/or agonist musculature-a maladaptive feature which potentially contributes to poorer single-limb hop performance. Measures of hamstring force steadiness in combination with traditional measures of peak hamstring strength provide valuable clinical information regarding knee joint function following ACL injury/ACLR.

In vitro biomechanical testing of anterior cruciate ligament reconstruction: traditional versus physiologically relevant load analysis

Various anterior cruciate ligament (ACL) graft-fixation devices exist. In this in vitro study a comparison of biomechanical characteristics of the cross-pin and button type fixation devices under practical rehabilitation loads was done. Forty bovine knees and hoof extensor tendons were harvested. After disarticulation, the femoral end of an ACL was prepared with either fixation, using the extensor tendon as graft. The mechanical test was either a single load to failure or load to failure after cycling loads. Twenty specimens were loaded to failure at a rate of 1mm/s, remaining specimens were cycled between 50 and 250 N for 1000 cycles then failure tested in a similar manner. Results show that both forms of fixation are able to withstand loads that exceed those observed in performing functional activities. Activity-specific stiffness (loads comparable to walking, jogging and stair descent) was lower than linear stiffness for both endobutton and cross-pin, without prior cycling. After cycling, activity-specific stiffness increased to linear stiffness values for the cross-pin for all activities. Thus, suggesting that the cross-pin provides a more rigid fixation after initial implantation over a wider range of activities, which would theoretically permit a more aggressive rehabilitation protocol and possibly an earlier return to regular activity. In contrast, activity-specific stiffness increased above linear stiffness values for the endobutton only under heavier loads (jogging and stair descent). Dynamic stiffness was higher and displacement lower for cross-pin throughout the cycle test. These results indicate, in ACL reconstruction, that graft complex stiffness should be considered at relevant loads only.

Cruciate ligament forces between short-step and long-step forward lunge

PURPOSE

The purpose of this study was to compare cruciate ligament forces between the forward lunge with a short step (forward lunge short) and the forward lunge with a long step (forward lunge long).

METHODS

Eighteen subjects used their 12-repetition maximum weight while performing the forward lunge short and long with and without a stride. EMG, force, and kinematic variables were input into a biomechanical model using optimization, and cruciate ligament forces were calculated as a function of knee angle. A two-factor repeated-measure ANOVA was used with a Bonferroni adjustment (P < 0.0025) to assess differences in cruciate forces between lunging techniques.

RESULTS

Mean posterior cruciate ligament (PCL) forces (69-765 N range) were significantly greater (P < 0.001) in the forward lunge long compared with the forward lunge short between 0 degrees and 80 degrees knee flexion angles. Mean PCL forces (86-691 N range) were significantly greater (P < 0.001) without a stride compared with those with a stride between 0 degrees and 20 degrees knee flexion angles. Mean anterior cruciate ligament (ACL) forces were generated (0-50 N range between 0 degrees and 10 degrees knee flexion angles) only in the forward lunge short with stride.

CONCLUSIONS

All lunge variations appear appropriate and safe during ACL rehabilitation because of minimal ACL loading. ACL loading occurred only in the forward lunge short with stride. Clinicians should be cautious in prescribing forward lunge exercises during early phases of PCL rehabilitation, especially at higher knee flexion angles and during the forward lunge long, which generated the highest PCL forces. Understanding how varying lunging techniques affect cruciate ligament loading may help clinicians prescribe lunging exercises in a safe manner during ACL and PCL rehabilitation.

Mechanical evaluation of cross pins used for femoral fixation of hamstring grafts in ACL reconstructions

The goal of this study was to test the mechanical strength of 4 different cross pins currently available for femoral fixation by loading each cross pin to failure as received and determine the effect of 1 million cycles of fatigue loading. Additionally, the strength of resorbable pins was tested after prolonged exposure to biologic conditions. Six implants each of the Arthrotek LactoSorb (Biomet, Warsaw, Indiana), Mitek RigidFix (DePuy Mitek Inc, Raynham, Massachusetts), Arthrotek Bone Mulch Screw (Biomet), cortical allograft, and control were tested for 3-point failure without prior loading and after cyclic loading between 50 to 200 N at 10 Hz for 1 million cycles. The bioabsorbable pins were placed in sterile water at 37°C and tested after 2, 4, and 6 months for 3-point failure strength. All implants tested without antecedent loading demonstrated adequate strength for initial fixation for hamstring grafts. During fatigue testing, RigidFix implants (n=6) failed at 18,893±8365 cycles (with a central deformation of 0.48±0.11 mm prior to fracture). All of the other implants tested endured 1 million cycles of loading (50-200 N) without fracture or 1.5 mm central deformation. Neither of the bioabsorbable pins demonstrated a significant change in yield strength after prolonged exposure to water. All implants tested demonstrated adequate strength for initial fixation of hamstring grafts. The metal and bone implants far exceed the strength required to sustain mechanical fixation until biological fixation occurs; both polymeric implants demonstrated that they maintained enough mechanical strength to achieve this goal.

Engineering orthopedic tissue interfaces

While a wide variety of approaches to engineering orthopedic tissues have been proposed, less attention has been paid to the interfaces, the specialized areas that connect two tissues of different biochemical and mechanical properties. The interface tissue plays an important role in transitioning mechanical load between disparate tissues. Thus, the relatively new field of interfacial tissue engineering presents new challenges--to not only consider the regeneration of individual orthopedic tissues, but also to design the biochemical and cellular composition of the linking tissue. Approaches to interfacial tissue engineering may be distinguished based on if the goal is to recreate the interface itself, or generate an entire integrated tissue unit (such as an osteochondral plug). As background for future efforts in engineering orthopedic interfaces, a brief review of the biology and mechanics of each interface (cartilage-bone, ligament-bone, meniscus-bone, and muscle-tendon) is presented, followed by an overview of the state-of-the-art in engineering each tissue, including advances and challenges specific to regenerating the interfaces.

Hamstring strength recovery after hamstring tendon harvest for anterior cruciate ligament reconstruction: a comparison between graft types

PURPOSE

The purpose of this study was to investigate hamstring strength after harvest of 1 or 2 hamstring tendons for anterior cruciate ligament reconstruction.

METHODS

We recruited 50 individuals who had returned to regular sporting activity to participate in a comparative study at a mean of 32.5 months after anterior cruciate ligament reconstructive surgery (30 in semitendinosus-gracilis group and 20 in semitendinosus group). Isokinetic hamstring strength (at 60 degrees/s and 180 degrees/s with the peak torque and torque produced at 60 degrees, 90 degrees, and 105 degrees of knee flexion recorded) and isometric hamstring strength (at 30 degrees, 90 degrees, and 105 degrees of knee flexion) were measured, and the standing knee flexion angle was used to evaluate functional hamstring strength recovery.

RESULTS

No significant differences between the groups were found in any of the isometric or isokinetic strength measures or in the standing knee flexion angle. No relation was found between the standing knee flexion angle and the isometric hamstring strength results obtained at 105 degrees of knee flexion (r(2) = 0.034).

CONCLUSIONS

These findings show that the choice of hamstring tendon graft-that is, semitendinosus alone or semitendinosus and gracilis-is unlikely to significantly influence postoperative hamstring strength outcomes in athletes returning to sports postoperatively. Both graft choices showed strength deficits of between 3% and 27% compared with the nonoperated limb, indicating that hamstring strength deficits persist despite successful completion of rehabilitation. The results also show that the standing knee flexion angle should not be used as a surrogate clinical measure of hamstring strength.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Cruciate ligament tensile forces during the forward and side lunge

BACKGROUND

Although weight bearing lunge exercises are frequently employed during anterior cruciate ligament and posterior cruciate ligament rehabilitation, cruciate ligament tensile forces are currently unknown while performing forward and side lunge exercises with and without a stride.

METHODS

Eighteen subjects used their 12 repetition maximum weight while performing a forward lunge and side lunge with and without a stride. A motion analysis system and biomechanical model were used to estimate cruciate ligament forces during lunging as a function of 0-90 degrees knee angles.

FINDINGS

Comparing the forward lunge to the side lunge across stride variations, mean posterior cruciate ligament forces ranged between 205 and 765N and were significantly greater (P<0.0025) in the forward lunge long at 40 degrees , 50 degrees , 60 degrees , 70 degrees , and 80 degrees knee angles of the descent phase and at 80 degrees , 70 degrees , 60 degrees knee angles of the ascent phase. There were no significant differences (P<0.0025) in mean posterior cruciate ligament forces between with and without stride differences across lunging variations. There were no anterior cruciate ligament forces quantified while performing forward and side lunge exercises.

INTERPRETATION

Clinicians should be cautious in prescribing forward and side lunge exercises during early phases of posterior cruciate ligament rehabilitation due to relatively high posterior cruciate ligament forces that are generated, especially during the forward lunge at knee angles between 40 degrees and 90 degrees knee angles. Both the forward and side lunges appear appropriate during all phases of anterior cruciate ligament rehabilitation. Understanding how forward and side lunging affect cruciate ligament loading over varying knee angles may help clinicians better prescribe lunging exercises in a safe manner during anterior cruciate ligament and posterior cruciate ligament rehabilitation.

Ankle morbidity after autogenous Achilles tendon harvesting for anterior cruciate ligament reconstruction

Although several alternative autografts with reduced morbidity of harvest site have been introduced, no donor site is free of morbidity concerns. The authors report on ankle status after autogenous Achilles tendon harvesting with a minimum 10-year follow-up. From October 1994 to October 1996, a consecutive series of 47 ankles underwent harvesting of the medial third or half of the ipsilateral autogenous Achilles tendon for primary anterior cruciate ligament reconstruction. Donor site statuses were evaluated using a modified Thermann's scale. Postoperative isokinetic muscle strength testing was performed, and magnetic resonance images of donor sites were available for selected patients. Thirty-three ankles in the 32 patients were followed for more than 10 years. There were 27 men (84%) and 5 women (16%) with a mean age of 31 years (range 16-52 years) at the time of surgery. The mean duration of follow-up was 12 years and 1 month (range 10 years and 5 months to 13 years and 4 months). Mean postoperative modified Thermann's scale score was 87 (range 45-95; SD 14.3). Twenty-five (76%) ankles achieved very good or good results. A slight decrease in calf circumference <1 cm was seen in the ten ankles, 1-2 cm in the four ankles. Nine ankles were mildly hypersensitive to meteorological changes. Peak torque of ankle plantar flexion was slightly lower on the index limb at both velocities in nine selected patients who carried out performance tests. However, there were no significant differences (5.2% at 30 degrees /s and 2.7% at 120 degrees /s, P = n.s. and P = n.s.). Of the 12 available follow-up magnetic resonance images, the average cross-sectional area of the remaining tendon was 82.01 mm(2) (range 69.05-107.35; SD 10.3), and their average thickness was 7.4 mm (range 6-10.35; SD 1.1). After a minimum 10-year follow-up, the harvesting of autogenous Achilles tendons was not found to significantly jeopardize ankle status. However, it also could not be independent of donor morbidity as an alternative. The level of evidence was retrospective level IV, as a therapeutic study.

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.

Augmentation of tendon-bone interface healing with low-intensity pulsed ultrasound

The capacity of low-intensity pulsed ultrasound to accelerate the integration of grafted tendon-within-bone tunnel was evaluated. The extensor digitorum longus tendons of 20 New Zealand white rabbits were transplanted into bone tunnels in both proximal tibias. One side was chosen randomly to receive low-intensity pulsed ultrasound. The other side served as control. Six rabbits each were sacrificed at 2 and 3 weeks postoperatively for biomechanical testing, and 2 rabbits each were sacrificed at 1, 3, 6, and 12 weeks postoperatively for histological study. At 2 weeks postoperatively, the mean maximal tensile strength in the ultrasound-treated group (30.676 N) was significantly stronger (P<.05) than the control group (17.924 N). There was no significant difference of the maximal tensile strength (33.674 vs 33.340 N; P=.753) between the ultrasound-treated and control groups at 3 weeks postoperatively. In the ultrasound-treated group, the histological study revealed the interface filled with denser granulation tissue and diffuse perpendicular anchored fibers in the 1- and 3-week specimens, and interface new bone formation in the 6- and 12-week specimens. The biomechanical and histological studies demonstrated that the low-intensity pulsed ultrasound enhanced the healing of grafted tendon-to-bone tunnel in the early stages. Our findings indicate that low-intensity pulsed ultrasound is a potentially promising mechanical tool to accelerate early tendon healing to bone tunnel.

Dynamic restraint capacity of the hamstring muscles has important functional implications after anterior cruciate ligament injury and anterior cruciate ligament reconstruction

OBJECTIVE

The purpose of this study was to investigate the relation between knee functionality of anterior cruciate ligament deficient (ACLD) and anterior cruciate ligament reconstruction (ACLR) patients and hamstring antagonist torque generated during resisted knee extension.

DESIGN

Cross-sectional.

SETTING

Laboratory based.

PARTICIPANTS

Male ACLD subjects (n=10) (18-35 y) and 27 matched males who had undergone ACLR (14 patella tendon [PT] grafts and 13 combined semitendinosus/gracilis tendon grafts).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Knee functionality was rated (0- to 100-point scale) by using the Cincinnati Knee Rating System. Using electromyography data from the semitendinosus (ST) and biceps femoris muscles, we created a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10 degrees intervals from 80 degrees to 10 degrees knee flexion.

RESULTS

Pearson product-moment correlations revealed that more functional ACLD subjects generated significantly (P<.05) higher hamstring antagonist torque throughout knee extension. In contrast, more functional PT subjects produced significantly lower hamstring antagonist torque at 80 degrees to 70 degrees knee flexion, whereas no significant associations were found between hamstring antagonist torque and knee functionality for the ST/gracilis tendon subjects.

CONCLUSIONS

An increased hamstring antagonist torque generated by the more functional ACLD subjects, reflective of increased hamstring contractile force, is thought to represent a protective mechanism to compensate for mechanical instability. The restoration of anterior knee stability through ACLR negates the need for augmented hamstring antagonist torque.

Prospective comparison of auto and allograft hamstring tendon constructs for ACL reconstruction

Although allograft use for primary anterior cruciate ligament reconstruction has continued to increase during the last 10 years, concerns remain regarding the long-term function of allografts (primarily that they may stretch with time) and clinical efficacy compared with autograft tendons. We attempted to address these issues by prospectively comparing identical quadrupled hamstring autografts with allograft constructs for primary anterior cruciate ligament reconstruction in patients with a minimum followup of 3 years. Eighty-four patients (37 with autografts and 47 with allografts) were enrolled; the mean followup was 52 +/- 11 months for the autograft group and 48 +/- 8 months for the allograft group. Outcome measurements included objective and subjective International Knee Documentation Committee scores, Lysholm scores, Tegner activity scales, and KT-1000 arthrometer measurements. The two cohorts were similar in average age, acute or chronic nature of the anterior cruciate ligament rupture, and incidence of concomitant meniscal surgeries. At final followup, we found no difference in terms of Tegner, Lysholm, KT-1000, or International Knee Documentation Committee scores. Five anterior cruciate ligament reconstructions failed: three in the autograft group and two in the allograft group. Our data suggest laxity is not increased in allograft tendons compared with autografts and clinical outcome scores 3 to 6 years after surgery are similar.

LEVEL OF EVIDENCE

Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Primary versus single-stage revision anterior cruciate ligament reconstruction using autologous hamstring tendon grafts: a prospective matched-group analysis

BACKGROUND

There is a low level of evidence about clinical results after anterior cruciate ligament (ACL) revision reconstruction using autologous hamstring tendon grafts.

HYPOTHESIS

Anterior cruciate ligament revision reconstruction improves knee stability but shows inferior results for functional and subjective outcome and knee stability compared with primary reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Between October 1997 and July 2005, 166 single-stage or 2-stage revision ACL reconstructions were done using different graft types. One hundred twenty-four cases underwent a single-stage revision reconstruction with autologous hamstring tendon grafts. At the time of data analysis, 67 cases fulfilled the criteria of minimum 2-year follow-up. Five patients were lost to follow-up (follow-up rate, 91%). Four patients (6%) who experienced graft rupture were counted as failures but not subjected to further detailed analysis. Because of loss to follow-up and exclusion criteria (n = 12), 50 patients were included in the study. For a comparative matched-group analysis, patients with a primary hamstring tendon graft ACL reconstruction were selected out of a database with minimum 2 years' follow-up (N = 284). Patients were followed using the International Knee Documentation Committee (IKDC) and Lysholm scores, KT-1000 arthrometer testing, and additional functional tests.

RESULTS

Four of 62 available patients (6.5%) in the revision group experienced graft failure, which was comparable to 16 of 284 (5.6%) in the primary reconstruction group. When the 2 matched groups of 50 patients were further compared, postoperative IKDC results showed no significant differences between groups. The manual maximum KT-1000 arthrometer side-to-side difference was 2.1 +/- 1.6 mm for the revision group and 2.2 +/- 1.1 mm for the primary reconstruction group. The Lysholm score was significantly better in the primary reconstruction group (P = .014). The incidence of postoperative positive pivot-shift test results was not significantly different. The primary reconstruction group showed significantly less extension deficits. Functional testing revealed significantly better results for the primary reconstruction group for stair climbing, squatting, knee bending, and duck walk.

CONCLUSIONS

In our patient series, primary ACL reconstruction showed significantly better results in Lysholm score, although the IKDC score and objective knee stability showed no significant difference between the groups. Thus, parameters other than measurable knee stability must be responsible for the inferior results of the revision reconstruction group.

Patellar tendon or semitendinosus tendon autografts for anterior cruciate ligament reconstruction: a prospective, randomized study with a 7-Year follow-up

BACKGROUND

The aim of the study was to compare the results after arthroscopic anterior cruciate ligament (ACL) reconstruction using central-third bone-patellar tendon-bone (BTB) autografts and triple/quadruple semitendinosus (ST) autografts.

HYPOTHESIS

In the long-term, ACL reconstruction using BTB autografts will render more donor-site problems than ST autografts.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A randomized series of 71 patients (22 women and 49 men) with a unilateral ACL rupture who underwent reconstructive surgery were included in the study. The BTB graft was used in 34 patients (BTB group) and the ST-tendon graft was used in 37 patients (ST group). The patients were examined a median of 86 months (range, 68 to 114 months) after the reconstruction.

RESULTS

Sixty-eight of 71 patients (96%) were examined at follow-up. The clinical assessments at follow-up revealed no significant differences between the BTB group and the ST group in terms of the Lysholm score, Tegner activity level, International Knee Documentation Committee evaluation system, 1-legged hop test, KT-1000 arthrometer laxity measurements, manual Lachman test, and range of motion. A significant improvement was seen in both groups compared with the preoperative values in terms of most clinical assessments. Donor-site morbidity in the form of knee-walking ability, kneeling ability, and area of disturbed anterior knee sensitivity revealed no significant differences between the groups.

CONCLUSION

Seven years after ACL reconstruction, the subjective and objective outcomes were similar after using the central-third BTB autograft and triple/quadruple ST autograft. Furthermore, no difference in terms of donor-site morbidity was found between the 2 groups.

Reconstruction of the anterior cruciate ligament: dynamic strain evaluation of the graft

The study is focused on the biomechanical aspects of the anterior cruciate ligament (ACL) reconstruction procedures with an emphasis on evaluating the dynamic strain of materials commonly used for this purpose. Separate and multiple, equally tensioned strands of hamstring grafts used for the reconstruction of the ACL were biomechanically tested and compared to original ACL and bone-patellar tendon-bone (BPTB) grafts, using tissue samples from cadavers. The study was focused on measuring such material properties as the strength, stiffness, maximum load, and elongation at maximum load of the original ACL, BPTB graft, and single tendon hamstring (gracilis and semitendinosus) grafts, continued by double strands and finally by four-strand graft (STG) evaluation. Fresh-frozen cadaveric knees were used, which had been clamped and tensioned equally. The measurement was performed by drop-weight testing, using a Laser Doppler Vibrometer as a basic sensor of the dynamic movements of the gripping clamps, with parallel correlation by a piezoelectric transducer. The grafts for experiments were obtained from 21-paired knees. The measurement was performed at room temperature (21 degrees C) after 24 h of thawing at 4 degrees C. All the specimens were measured for their response to the dynamic tensile load. The maximum strength values were obtained and calculated for the appropriate section area of the specimen. The tensioned strands of the original ACL showed a maximum average load of 1,246 +/- 243 N in the section area of about 30 mm(2) (max. stress 41.3 MPa); the strands of BPTB grafts showed values of 3,855 +/- 550 N in the section area of 80 mm(2) (max. stress 40.6 MPa); the gracilis tendons showed 925 +/- 127 N in the section area of 10 mm(2) (max. stress 95.1 MPa) and the semitendinosuss yielded a result of 2,050 +/- 159 N in the area of 20 mm(2) (max. stress 88.7 MPa). Of all the materials, the original ACL have the lowest strength and stiffness in respect of their biomechanical properties. BPTB grafts showed a slightly higher value of maximum stress, while both the gracilis and semitendinosus tendons showed double the value of maximum load per section area-tensile stress. Two- and four- combined hamstring strands clamped together and equally tensioned with a drop-weight had the combined tensile strength properties of the individual strands within the estimated range of measurement errors. No significant changes in maximum loads/stresses were observed under impact loading conditions. The results of this study demonstrate that equally tensioned four-strand hamstring-tendon grafts have higher initial tensile properties than those in other varieties of samples. From a biomechanical point of view, they seem to be a reasonable alternative procedure for ACL reconstruction.

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.

Hamstring tendons regeneration after ACL reconstruction: an overview

Despite the long lasting research the ideal method of reconstructing the ACL has not been found so far. The last year's attention has shifted to the use of the multistrand hamstring tendon grafts. High ultimate tensile load, multiple-bundle replacement that better approximates the anatomy of the normal ACL and low donor site morbidity are the main advantages of this ACL replacement graft. These theoretical advantages have been multiplied when surprisingly studies have shown that semitendinosus and gracilis tendons actually regenerate after harvesting for use as ACL autografts. In this review article we summarize the current knowledge concerning the hamstring regeneration and we focus on issues that have clinical relevance or issues that have not been answered so far.