Digital Extensor Tendon Research Articles

Viscoelasticity of Tendons Under Transverse Compression.

Tendons are highly anisotropic and also viscoelastic. For understanding and modeling their 3D deformation, information is needed on their viscoelastic response under off-axis loading. A study was made, therefore, of creep and recovery of bovine digital extensor tendons when subjected to transverse compressive stress of up to ca. 100 kPa. Preconditioned tendons were compression tested between glass plates at increasing creep loads. The creep response was anomalous: the relative rate of creep reduced with the increasing stress. Over each ca. 100 s creep period, the transverse creep deformation of each tendon obeyed a power law dependence on time, with the power law exponent falling from ca. 0.18 to an asymptote of ca. 0.058 with the increasing stress. A possible explanation is stress-driven dehydration, as suggested previously for the similar anomalous behavior of ligaments. Recovery after removal of each creep load was also anomalous. Relative residual strain reduced with the increasing creep stress, but this is explicable in terms of the reducing relative rate of creep. When allowance was made for some adhesion occurring naturally between tendon and the glass plates, the results for a given load were consistent with creep and recovery being related through the Boltzmann superposition principle (BSP). The tendon tissue acted as a pressure-sensitive adhesive (PSA) in contact with the glass plates: explicable in terms of the low transverse shear modulus of the tendons.

Single harvesting in the all-inside graft-link technique: is the graft length crucial for success? A biomechanical study

BackgroundThe all-inside graft-link technique for anterior cruciate ligament reconstruction is performed with two cortical suspension devices with adjustable loops on both femur and tibia. This technique requires meticulous graft preparation. The aim of this study was to biomechanically test three different graft configurations resulting from differences in initial graft length.Materials and methodsThirty bovine digital extensor tendons were arranged in three different ways: “half-quadrupled”, “tripled” and “quadrupled”. The final graft length was 65–75 mm. The specimens were fixed vertical to the loading axis of a tensile testing machine. After a static pre-conditioning of 50 N for 5 min, a load to failure test was performed and data regarding the ultimate failure load (UFL), the stiffness and mode of failure were recorded.ResultsThe evaluation of UFL showed a significant differences between group means as determined by one-way analysis of variance (F = 21.92, p = 0.002). Post hoc comparisons showed a significantly better UFL of “tripled” (p = 0.007) and “quadrupled” preparations (p = 0.014) compared to the “half-quadrupled” configuration, with no significant differences between “tripled” and “quadrupled” grafts (p = 0.061). No significant differences were found when evaluating the stiffness between the groups. Failure occurred by tendon slippage across the suture in all specimens.ConclusionThe “quadrupled” tendon achieved the best UFL, with even the “tripled” configuration having sufficient biomechanical characteristics to withstand the loads experienced during early rehabilitation. For this reason, with a total semitendinosus length of less than 260 mm it could be better to “triple” instead of “half-quadruple” it to achieve better performance of the graft.

Differential Adhesion Selection for Enrichment of Tendon-Derived Progenitor Cells DuringIn VitroCulture

Preplating, a technique used to separate rapidly adherent fibroblasts from the less-adherent progenitor cells, has been used successfully to isolate skeletal muscle-derived stem cells. The objective of this study was to determine if preplating could also be applied to enrich tendon-derived progenitor cells (TDPCs) before monolayer expansion. Cell suspensions obtained by collagenase digestion of equine lateral digital extensor tendon were serially transferred into adherent plates every 12 h for 4 days. TDPC fractions obtained from initial (TPP0), third (TPP3), and seventh (TPP7) preplate were passaged twice and used for subsequent analyses. Growth/proliferation and basal tenogenic gene expression of the three TDPC fractions were largely similar. Preplating and subsequent monolayer expansion did not alter the immunophenotype (CD29(+), CD44(+), CD90(+), and CD45(-)) and trilineage differentiation capacity of TDPC fractions. Overall, TDPCs were robustly osteogenic, but exhibited comparatively weak adipogenic and chondrogenic capacities. These outcomes indicate that preplating does not enrich for tendon-derived progenitors during in vitro culture, and "whole tendon digest"-derived cells are as appropriate for cell-based therapies.

Fascicles and the interfascicular matrix show adaptation for fatigue resistance in energy storing tendons

Tendon is composed of rope-like fascicles, bound together by interfascicular matrix (IFM). Our previous work shows that the IFM is critical for tendon function, facilitating sliding between fascicles to allow tendons to stretch. This function is particularly important in energy storing tendons, which experience extremely high strains during exercise, and therefore require the capacity for considerable inter-fascicular sliding and recoil. This capacity is not required in positional tendons. Whilst we have previously described the quasi-static properties of the IFM, the fatigue resistance of the IFM in functionally distinct tendons remains unknown. We therefore tested the hypothesis that fascicles and IFM in the energy storing equine superficial digital flexor tendon (SDFT) are more fatigue resistant than those in the positional common digital extensor tendon (CDET). Fascicles and IFM from both tendon types were subjected to cyclic fatigue testing until failure, and mechanical properties were calculated. The results demonstrated that both fascicles and IFM from the energy storing SDFT were able to resist a greater number of cycles before failure than those from the positional CDET. Further, SDFT fascicles and IFM exhibited less hysteresis over the course of testing than their counterparts in the CDET. This is the first study to assess the fatigue resistance of the IFM, demonstrating that IFM has a functional role within tendon and contributes significantly to tendon mechanical properties. These data provide important advances into fully characterising tendon structure-function relationships. Statement of SignificanceUnderstanding tendon-structure function relationships is crucial for the development of effective preventative measures and treatments for tendon injury. In this study, we demonstrate for the first time that the interfascicular matrix is able to withstand a high degree of cyclic loading, and is specialised for improved fatigue resistance in energy storing tendons. These findings highlight the importance of the interfascicular matrix in the function of energy storing tendons, and potentially provide new avenues for the development of treatments for tendon injury which specifically target the interfascicular matrix.

Dorsal Arthroscopic Approach and Intra-Articular Anatomy of the Bovine Antebrachiocarpal and Middle Carpal Joints.

To determine arthroscopic approaches to the dorsal synovial compartments of the antebrachiocarpal and middle carpal joints in adult cattle, and to describe the arthroscopic intra-articular anatomy from each approach. Ex vivo study. Six fresh adult bovine cadavers. Two carpi were injected with latex and dissected to determine the ideal location for arthroscopic portals. Arthroscopy of the antebrachiocarpal and middle carpal joints of 10 carpi was then performed. The dorsolateral approach was made between the extensor carpi radialis and common digital extensor tendons. The dorsomedial approach was made medial to the extensor carpi radialis tendon, midway between the distal radius and proximal row of carpal bones (antebrachiocarpal joint) and midway between the two rows of carpal bones (middle carpal joint), with the joint in flexion. Arthroscopy of the antebrachiocarpal joint allowed visualization of the distal radius, proximal aspect of the radial, intermediate and ulnar carpal bones, and a palmar ligament located between the radius and the intermediate carpal bone. The approach to the middle carpal joint allowed visualization of the distal aspect of the radial, intermediate, and ulnar carpal bones, the proximal aspect of the fourth and fused second and third carpal bones and an interosseous ligament. The most lateral articular structures (lateral glenoid cavity of the distal radius, ulnar carpal and fourth carpal bones) were difficult to assess. Dorsal approaches to the antebrachiocarpal and middle carpal joints allowed visualization of most intra-articular dorsal structures in adult cattle.

Arthroscopic Removal of Large Extensor Process Fragments in 18 Friesian Horses: Long-Term Clinical Outcome and Radiological Follow-Up of the Distal Interphalangeal Joint.

Report long-term clinical and radiological follow-up in horses after removal of large extensor process fragments occupying >25% of the joint surface of the distal interphalangeal joint (DIJ). Retrospective case series. Friesian horses (n=18) that underwent arthroscopic removal of a large extensor process fragment. Arthroscopic examination of the DIJ was performed in dorsal recumbency with the affected foot in extension using routine portals. Visualization of the fragment was improved using motorized synovial resectors. A dissection plane between the common digital extensor tendon and the extensor process fragment was created using sharp lever instruments, in some cases aided by motorized burrs and radiofrequency ligament dissection. The fragment was removed piecemeal using Ferris-Smith rongeurs. Medical records, preoperative and postoperative radiographs, and owner surveys were reviewed for case details and outcome. The technique described allowed removal of the large fragment in all 18 horses. Of the 17 horses where long-term clinical follow-up was available, 14 were used as intended and 3 kept some degree of lameness. The angle between the remodeled extensor process and the dorsal surface of the distal phalanx was increased and subchondral bone remodeling at the fragment bed was noted on postoperative lateromedial radiographs. Arthroscopic removal is a good treatment option for horses with large extensor process fragmentation with a good long-term outcome. Remodeling of the remaining extensor process and the subchondral new bone formation in the fragment bed can occur with functional recovery.

Distribution of proteins within different compartments of tendon varies according to tendon type.

Although the predominant function of all tendons is to transfer force from muscle to bone and position the limbs, some tendons additionally function as energy stores, reducing the energetic cost of locomotion. To maximise energy storage and return, energy‐storing tendons need to be more extensible and elastic than tendons with a purely positional function. These properties are conferred in part by a specialisation of a specific compartment of the tendon, the interfascicular matrix, which enables sliding and recoil between adjacent fascicles. However, the composition of the interfascicular matrix is poorly characterised and we therefore tested the hypothesis that the distribution of elastin and proteoglycans differs between energy‐storing and positional tendons, and that protein distribution varies between the fascicular matrix and the interfascicular matrix, with localisation of elastin and lubricin to the interfascicular matrix. Protein distribution in the energy‐storing equine superficial digital flexor tendon and positional common digital extensor tendon was assessed using histology and immunohistochemistry. The results support the hypothesis, demonstrating enrichment of lubricin in the interfascicular matrix in both tendon types, where it is likely to facilitate interfascicular sliding. Elastin was also localised to the interfascicular matrix, specifically in the energy‐storing superficial digital flexor tendon, which may account for the greater elasticity of the interfascicular matrix in this tendon. A differential distribution of proteoglycans was identified between tendon types and regions, which may indicate a distinct role for each of these proteins in tendon. These data provide important advances into fully characterising structure–function relationships within tendon.

Slab fractures of the third tarsal bone: Minimally invasive repair using a single 3.5 mm cortex screw placed in lag fashion in 17 Thoroughbred racehorses.

A technique for minimally invasive repair of slab fractures of the third tarsal bone has not previously been reported. Results of third tarsal bone slab fracture repair in Thoroughbred racehorses are lacking. To report the outcomes of repair of uniplanar frontal slab factures of the third tarsal bone using a single 3.5 mm cortex screw in lag fashion. Retrospective case series. Case records of horses that had undergone this procedure were reviewed. Seventeen horses underwent surgery. Eighteen percent of cases had wedge shaped third tarsal bones. A point midway between the long and lateral digital extensor tendons and centrodistal and tarsometatarsal joints created a suitable entry site for implants. The fracture location, configuration and curvature of the third tarsal bone and associated joints requires a dorsolateral proximal-plantaromedial distal trajectory for the screw, which was determined by preplaced needles. There were no complications and fractures healed in all cases at 4-6 months post surgery. Seventy-nine percent of horses returned to racing and, at the time of reporting, 3 are in post operative rehabilitation programmes. The technique reported provides a safe, appropriate and repeatable means of repairing slab fractures of the third tarsal bone. Surgical repair is a viable alternative to conservative management.

Transverse Compression of Tendons.

A study was made of the deformation of tendons when compressed transverse to the fiber-aligned axis. Bovine digital extensor tendons were compression tested between flat rigid plates. The methods included: in situ image-based measurement of tendon cross-sectional shapes, after preconditioning but immediately prior to testing; multiple constant-load creep/recovery tests applied to each tendon at increasing loads; and measurements of the resulting tendon displacements in both transverse directions. In these tests, friction resisted axial stretch of the tendon during compression, giving approximately plane-strain conditions. This, together with the assumption of a form of anisotropic hyperelastic constitutive model proposed previously for tendon, justified modeling the isochronal response of tendon as that of an isotropic, slightly compressible, neo-Hookean solid. Inverse analysis, using finite-element (FE) simulations of the experiments and 10 s isochronal creep displacement data, gave values for Young's modulus and Poisson's ratio of this solid of 0.31 MPa and 0.49, respectively, for an idealized tendon shape and averaged data for all the tendons and E = 0.14 and 0.10 MPa for two specific tendons using their actual measured geometry. The compression load versus displacement curves, as measured and as simulated, showed varying degrees of stiffening with increasing load. This can be attributed mostly to geometrical changes in tendon cross section under load, varying according to the initial 3D shape of the tendon.

Silfverskiold technique combined with dynamic splinting for treatment of digital extensor tendon rupture in zones III and IV

Objective To investigate the clinical results of Silfverskiold suture combined with dynamic splinting in treating extensor digitorum tendon rupture in zones Ⅲ and Ⅳ. Methods Between March 2010 and October 2013, a total of 67 patients with 85 extensor digitorum tendon lacerations in zones Ⅲ and Ⅳ were included in this study. The tendons were repaired using Silfverskiold technique which was a combination of modified Kessler core suture and running cross-stitch epitendinous suture. The patients began controlled exercise within seven days postoperatively wearing a dynamic extension splint. Active flexion and passive extension of the fingers were repeated ten times per hour. After three weeks, the dynamic splint was removed and the patients began active finger flexion and extension. Protective static splinting was continued with the interphalangeal joints in full extension between exercises and during the night for another 2 weeks. Results Postoperative follow-up period ranged from 3 to 6 months, with an average of 4 months. Forty-two of the 67 patients regained full range of motion within 9 weeks postoperatively. At the final follow-up evaluation, according to Miller′s criteria, the results were graded as excellent in 50 fingers, good in 30 fingers and fair in 5 fingers. The overall satisfactory rate was 94.1%. There was no rupture of the repaired tendons. Conclusion Silfverskiold suture combined with dynamic splinting is an effective treatment method for extensor digitorum tendon lacerations in zones Ⅲ and Ⅳ. It is safe and reliable. Key words: Tendon injuries; Rehabilitation; Silfverskiold technique; Dynamic splinting

FEASIBILITY FOR ULTRASOUND-GUIDED INJECTION OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES.

Desmitis of the collateral ligament of the distal interphalangeal joint is a cause of lameness in performance horses. The objective of this prospective, experimental, ex vivo feasibility study was to evaluate the success of ultrasound-guided injection of the collateral ligaments of the distal interphalangeal joint in the equine forelimb. Seventy-six ultrasound-guided dye injections of the collateral ligament of the distal interphalangeal joint were performed on horses' cadaver limbs. The hooves were sectioned transversely to verify the location of the dye relative to the collateral ligaments and surrounding structures. Evaluations of transverse sections were performed independently by two experienced observers. A scoring system was used to assess injection of the collateral ligament of the distal interphalangeal joint at the proximal, middle, and distal aspect over the length of the ligament. The collateral ligament was injected at any point in 97.4% of cases. The ligament was injected over the entire scored length in 43.2% of cases (32/74), over two scored length areas in 45.9% of cases (34/74), and in one area in 10.8% of cases (8/74). The distal interphalangeal joint and the common digital extensor tendon were also injected in 81.6% (62/76) and 43.4% (33/76) of the cases, respectively. Use of the ultrasound had a positive and negative predictive value of 98% and 9%, respectively. In this study, ultrasound guidance was useful for confirming injection of the collateral ligament of the distal interphalangeal joint but did not prevent injecting the distal interphalangeal joint and the common digital extensor tendon.

Lipoma of the long digital extensor tendon sheath in a horse

SummaryThis paper describes the occurrence of a lipoma associated with the long digital extensor tendon sheath at the level of the tarsus in a 5‐month‐old female Thoroughbred. Radiographic and ultrasonographic images were interpreted as being an atypically located lipoma. Its position and character have some similarities to lipoma arborescens, which is reported to occur in and around human joints and tendon sheaths. Surgical removal is considered to be the treatment of choice.

Tendon-bone interface healing using an injectable rhBMP-2-containing collagen gel in a rabbit extra-articular bone tunnel model.

This study examines the hypothesis that injectable collagen gel can be an effective carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2)'s localization to the healing tendon-bone interface. In 36 mature New Zealand White rabbits, the upper long digital extensor tendon was cut and inserted into the proximal tibial bone tunnel. Then a rhBMP-2-containing collagen gel was injected into the tendon-bone tunnel interface, using a syringe. Histological and biomechanical assessments of the tendon-bone interface were conducted at 3 and 6 weeks after implantation. In vitro testing showed that the semi-viscous collagen gel at room temperature was transformed into a firm gel state at 37°C. The rhBMP-2 release profile showed that rhBMP-2 was released from the collagen gel for more than 28 days. In vivo testing showed that fibrocartilage and new bone are formed at the interface at 6 weeks after injection of rhBMP-2. On radiography, spotty calcification appeared and enthesis-like tissue was produced successfully in the tendon at 6 weeks after injection of rhBMP-2. Use of the viscous collagen gel and rhBMP-2 mixture increased the fusion rate between the bone tunnel and tissue graft. This study demonstrates that viscous collagen gel can be an effective carrier for rhBMP-2 delivery into surgical sites, and that the injectable rhBMP-2-containing collagen gel may be applied for the enhancement of tendon-bone interface healing in the future. Copyright © 2015 John Wiley & Sons, Ltd.

Tensile mechanical properties of human forearm tendons

Previous studies of the mechanical properties of tendons in the upper limb have used embalmed specimens or sub-optimal methods of measurement. The aim of this study was to determine the biomechanical properties of all tendons from five fresh frozen cadaveric forearms using updated methodology. The cross-sectional area of tendons was accurately measured using a laser reflectance system. Tensile testing was done in a precision servo-hydraulic device with cryo-clamp fixation. We determined that the cross-sectional area of some tendons is variable and directly influences the calculated material properties; visual estimation of this is unreliable. Data trends illustrate that digital extensor tendons possess the greatest tensile strength and a higher Young's modulus than other tendon types.

The interfascicular matrix enables fascicle sliding and recovery in tendon, and behaves more elastically in energy storing tendons

While the predominant function of all tendons is to transfer force from muscle to bone and position the limbs, some tendons additionally function as energy stores, reducing the cost of locomotion. Energy storing tendons experience extremely high strains and need to be able to recoil efficiently for maximum energy storage and return. In the equine forelimb, the energy storing superficial digital flexor tendon (SDFT) has much higher failure strains than the positional common digital extensor tendon (CDET). However, we have previously shown that this is not due to differences in the properties of the SDFT and CDET fascicles (the largest tendon subunits). Instead, there is a greater capacity for interfascicular sliding in the SDFT which facilitates the greater extensions in this particular tendon (Thorpe et al., 2012). In the current study, we exposed fascicles and interfascicular matrix (IFM) from the SDFT and CDET to cyclic loading followed by a test to failure. The results show that IFM mechanical behaviour is not a result of irreversible deformation, but the IFM is able to withstand cyclic loading, and is more elastic in the SDFT than in the CDET. We also assessed the effect of ageing on IFM properties, demonstrating that the IFM is less able to resist repetitive loading as it ages, becoming stiffer with increasing age in the SDFT. These results provide further indications that the IFM is important for efficient function in energy storing tendons, and age-related alterations to the IFM may compromise function and predispose older tendons to injury.

Transfer of the Fifth Finger to Replace an Amputated Thumb: A Preliminary Study.

Amputation of the thumb causes not only loss of significant functional use of the hand but also psychological and social problems. The procedures of toe-to-thumb transfer, pollicization, or metacarpal extension are recognized and well-documented options in thumb reconstruction. Although these techniques have been successfully applied, they have some disadvantages. This study aims to test the feasibility of the fifth finger for thumb reconstruction. The fifth finger was released following exploration of the digital artery, vein, nerve, and flexor and extensor tendons, including the flexor retinaculum. The digital vein and the extensor tendon of the fifth finger were separated at the level of the metacarpophalangeal joint. The proximal phalanx of the fifth finger was cut smoothly at the level of the metacarpophalangeal joint with a saw. The deep flexor tendons, digital arteries, and nerves were preserved. The proximal phalanx of the released fifth finger was fixed to the first metacarpal bone. The digital vein of the first finger was anastomosed to the digital vein of the fifth finger by microsurgery. Angiography was done after the transfer. Exploration till the flexor retinaculum enabled thumb transfer without any restriction of movement in all 10 cadaver fingers. The average total surgical time was 135 ± 12 minutes. Flow from both radial and ulnar arteries was demonstrated in the transferred fifth finger by angiography. The technique appears to be feasible for thumb reconstruction by preserving digital arteries and nerves in a relatively short time, but further important aspects have to be assessed in further clinical studies.

Ultrasonography of the distal limbs in Nellore and Girolando calves 8 to 12months of age.

BackgroundUltrasonography can be used anywhere and allows rapid, noninvasive differentiation of soft tissue structures of the musculoskeletal system. The objectives of this study were to describe the ultrasonographic appearance of the structures of the metacarpo-/metatarsophalangeal and the interphalangeal joints, the appearance of the growth plates of the distal metacarpus/metatarsus and of the proximal phalanx and to measure the cross-sectional dimensions of the DDFT and SDFT in Nellore and Girolando calves eight to 12 months of age.ResultsIn the longitudinal dorsal view the common digital extensor tendon and the digital extensor tendon were depicted as echogenic parallel fiber bundles located directly under the skin. The joint spaces appeared as anechoic interruptions of the hyperechogenic bone surfaces. The normal amount of synovial fluid could not be depicted. The growth plates were seen as anechoic interruptions of the bone surface proximal and distal to the fetlock joint space. In transverse sonograms of the distal palmar/plantar regions, the flexor tendons and branchs of the suspensory ligament were imaged as echogenic structures. The lumen of the digital flexor tendon sheath could not be imaged in these normal cattle. The thin digital distal annular ligament and the reversal of positions of the DDFT and SDFT could be appreciated. No significant differences were found between the cross-sectional measurements of the DDFT and the SDFT from Nellore and Girolando in any age, thoracic/pelvic limbs, right/left sides and lateral/medial digits.ConclusionsThe results of this study establish important ultrasonographic reference data of the normal structures of the distal limbs and the normal dimensions of the flexor tendons in Nellore and Girolando calves for use in clinical practice.

Long Digital Extensor Tendon Mineralization and Cranial Cruciate Ligament Rupture in a Dog

To report clinical and histopathologic features of long digital extensor (LDE) tendon mineralization with concurrent cranial cruciate ligament (CCL) rupture in a dog. Case report. 1.5-year-old, male castrated, English bulldog mix weighing 31.5 kg. Pre- and postoperative orthogonal radiographs, arthroscopic evaluation, arthrotomy with en bloc surgical excision, and histopathologic analysis of the excised LDE tendon. There was radiographic evidence of mineralization in the region of the proximal LDE and stifle instability suggestive of CCL rupture. Arthroscopy, and subsequent arthrotomy, showed complete tearing of the CCL and an intact but grossly thickened LDE. No evidence of avulsion or bony proliferation associated with the LDE was appreciated. Tibial plateau leveling osteotomy (TPLO) and tenectomy of the LDE returned the dog to normal weight-bearing. No evidence of ectopic mineralization in the affected limb or similar clinical signs in the contralateral limb have been observed in 12 months follow-up. LDE tenectomy followed by stabilization of the stifle by TPLO resulted in a functional outcome. Mineralization without concurrent avulsion of the LDE has not been reported in dogs; however, posterolateral tendon injury in people has been linked to knee instability and cruciate ligament rupture.

Radiographic and Computed Tomographic Anatomy of the Fetlock, Pastern and Coffin Joints of the Manus of the Donkey (Equus asinus)

The digit of the donkey as a draught animal is commonly susceptible to much affection. The purpose of the present study was to provide a detailed anatomic reference of radiographic and computed tomographic images in conjunction with cross and sagittal sections of the normal fetlock, pastern and coffin joints of the donkey for anatomists, surgeons and veterinary students. Eight adult donkeys of both sexes free from any joints affection were used in our study. The digit of two donkeys had undergone radiographic and computed tomographic scanning; the other donkey’s specimens were used to anatomical dissection and sectional anatomy. In the computed tomography (CT) of the fetlock joint all bone structures of the joint appeared also the soft tissue structures that could be identified and evaluated on the different soft tissue window planes included the common digital extensor tendon, lateral digital extensor tendon, superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), straight, oblique, and cruciate distal sesamoidean and intersesamoidean ligaments. For the pastern joint the structures that can be identified including the proximal phalanx, DDFT and digital cushion. In the coffin joint the collateral sesamoidean ligament (CSL) is difficult to identify on CT images.

Effect of suturing the femoral portion of a four-strand graft during an ACL reconstruction

A suture passed along the part of the graft that will be inserted into the femoral tunnel is widely used by surgeons, because it could prevent the graft sliding on the femoral fixation device during pulling from the tibial side. The aim of this study was to evaluate the biomechanical effects of suturing the intratunnel femoral part of the graft during an anterior cruciate ligament (ACL) reconstruction. Bovine digital extensor tendons and tibias were harvested from 20 fresh-frozen mature bovine knees ranging in age from 18 to 24months. Quadruple-strand bovine tendons were passed through the tibial tunnel and secured distally with a bioabsorbable interference screw. In one half of all grafts (N=10), the looped-over part of the graft was sutured in a whipstitch technique over a distance of 30mm (Group 1). In one half of all grafts (N=10), the looped-over part was left free from any suture (Group 2). The grafts were preconditioned at 50N for 10min, followed by cyclic loading at 1Hz between 50N and 250N for 1,000 cycles. Load-to-failure test was then carried out at a rate of 1mm/s. There was no statistically significant difference between mean stiffness at pullout and yield load between the two groups. In all specimens on Group 1, failure occurred following to partial breaking and then slipping of the tendons between the screw and the tunnel. Concerning Group 2, in six cases failure occurred as described for Group 1 specimens. In the remaining four cases, failure occurred entirely through the ligament mid-substance. Suturing in a whipstitch fashion the femoral portion of the graft doesn't affect the mechanical proprieties of the ACL graft. When suspension fixation device is used, suturing the looped-over part of the graft could be helpful in order to provide equal tension in all of the strands of the graft at time of tibial fixation.