Impact of tendon suturing on the interference fixation strength of quadrupled hamstring tendon grafts

Introduction

Interference screw fixation of soft tissue grafts has been a widely used fixation technique for cruciate ligament reconstruction. Suturing of the graft construct prior to graft fixation has been proposed to increase fixation strength; however, the effect on mechanical properties has not been well characterized. The goal of this study was to determine whether uniform suturing of the tendon graft affects (1) ultimate fixation strength of the hamstring tendon graft and (2) motion of the tendon in the bone tunnel during cyclic loading when comparing sutured grafts vs. unsutured grafts.

Method

Eight pairs of matched mature porcine tibias (age <2 years) and eight paired fresh-frozen human quadrupled hamstring tendon grafts were used. One quadrupled graft from each pair was placed into one of two groups. In the group A a single cerclage suture 3 cm from the doubled end of the graft was placed to join the four tendon strands. In group B a heavy suture was used to tightly unite the four strands of tendon graft to provide a better grip for the interference screw during fixation. The grafts were placed in tibial bone tunnels that matched the graft’s diameter and fixed with an interference screw. The looped end of the graft and the attached tibia were rigidly fixed in a material testing machine. The graft constructs were subjected to 100 cycles of 20–250 N load, followed by a load-to-failure test. In addition, a motion analysis system was used during cyclic testing to better determine the amount of elongation at the graft–tunnel interface. Statistical analysis of the failure load and stiffness and the overall elongation following cyclical loading was performed using the Wilcoxon rank sum test. Level of significance was set at p < 0.05.

Results

Elongation at the tendon–bone interface during sub-maximal cyclic loading was 2.4 ± 1.4 mm (unsutured) vs. 2.0 ± 0.7 mm (sutured) (p > 0.05). Failure load of the grafts without sutures (634 ± 86 N) was significantly lower than with the sutures (837 ± 183 N). Ultimate stiffness of group A (283 ± 34 N/mm) was lower than that of group B (331 ± 51 N/mm); however, this was not statistically significant (p = 0.051).

Conclusion

This study confirms that suturing of the graft construct before interference screw fixation may increase ultimate failure load. However, an improvement of structural properties in response to cyclic loading with sub-maximal loads could not be confirmed. Clinicians using interference screw fixation may suture the graft to improve fixation strength; however, suturing does not appear to allow a more aggressive rehabilitation after surgery.     

Whip stitch versus grasping suture for tendon autograft

Purpose

During tendon autograft harvest, either a grasping suture or traditional whip stitch can be used to grasp tendon prior to definitive bone fixation. Their grip strength has not, to our knowledge, been compared. This article compares a needle-free suture technique to a standard whip stitch by testing grip strength in vitro.

Methods

Twelve uniform ovine flexor tendons were prepared; six tendons with a standard, non-locking whip stitch and six tendons with a grasping suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Load/displacement curves were generated, and qualitatively assessed and peak loads were compared.

Results

There were no significant differences between the groups in tendon length or diameter. Modes of failure between the groups, as characterised by the load/displacement curves, were quite distinct. Peak load to failure was lower in the utility suture group (mean peak load at failure 121.28 N) than the whip stitch group (mean peak load to failure 188.82 N). All failures in the utility suture group occurred when the suture snapped.

Conclusions

The grasping suture described here is weaker than a standard whip stitch but may be sufficiently strong to harvest and handle tendon autograft. A standard whip stitch remains the choice for definitive graft fixation.     

Primärstabilität des Kapsel-Labrum-Komplexes nach Rekonstruktion mit Mitek-Bioknotless-Fadenankern am humanen Schulterkadavermodell

Background

This study examines the postoperative stability of the Mitek Bioknotless anchor system with biomechanical draw-out pulling in human cadaver shoulders.

Method

With simulation of anterior shoulder dislocation a test group (n=10, Ø 45 years) was tested against a native group (n=8, Ø 47 years). All shoulders were dissected up to the passive stabilizers. In the test group an artificial Bankart lesion was created and repaired with three Mitek Bioknotless anchors. The humeri of both groups were fixed in 60° glenohumeral abduction and 90° external rotation and then dislocated in a ventral direction. For evaluation purposes the ultimate draw-out strength, mode of failure, translation of humeral head, capsular slope, and bone density in the test group were measured.

Results

In the test group the ultimate strength was a median of 937 N (min. 554 N, max. 1,294 N) with 28 bony anchor dislocations, 1 suture rupture, and 1 capsular rupture, and in the native group with 6 Bankart and 2 HAGL lesions it was 1,214 N (708 N, 1,471 N). The bone density showed a positive correlation to the draw-out strength regarding cortical density and total density.

Conclusion

Regarding the high draw-out strength the Mitek Bioknotless anchor system provides enough stability for early functional treatment.     

A single dose of platelet-rich plasma improves the organization and strength of a surgically repaired rotator cuff tendon in rats

Introduction

Rotator cuff tear (RCT) is a common cause of pain and disability among adults. Platelet-rich plasma (PRP) is a fraction of whole blood containing concentrated growth factors and proteins important for tissue healing. This study aimed at investigating the effects of local autologous PRP injection on repaired rotator cuff (RC) tendon repair in rats.

Methods

Following experimental RCT and suturing, 44 Wistar rats were randomly allocated into two groups: (1) RC repair only (controls); (2) RC repair + PRP administration-shoulders were treated with intra-articular PRP immediately after the repair. Animals were killed after 3 weeks and tendon, were tested biomechanically in tension (12 rats/group). The remaining tendons (10 rats/group) were stained using hematoxylin and eosin and Picro-sirius Red. Histological analysis evaluated the cellular aspects of the repair tissue.

Results

PRP administration following experimental RC tear and suture resulted in a significantly higher maximal load (p < 0.001) and stiffness (p < 0.005) as compared to non-treated animals. Bonar score of PRP-treated tendons was significantly better (p = 0.018) than the control group. Collagen birefringence was significantly higher in PRP shoulders (p = 0.002), indicating improved organization. Vascularity scores were similar in both groups.

Conclusion

Application of a single dose autologous PRP in adjunct to surgical repair resultes in improved tendon-to-bone healing, assessed by histological and biomechanical testing in a rat model of acute RCT, when tested at 3 weeks compared to controls. Further studies will be essential to determine the role of PRP in clinical practice.     

Evaluation of a New Knotless Suture Anchor Repair in Acute Achilles Tendon Ruptures: A Biomechanical Comparison of Three Techniques

Acute ruptures of the Achilles tendon are a common injury, and debate has continued in published studies on how best to treat these injuries. Specifically, controversy exists regarding the surgical approaches for Achilles tendon repair when one considers percutaneous versus open repair. The present study investigated the biomechanical strength of 3 different techniques for Achilles tendon repair in a cadaveric model. A total of 36 specimens were divided into 3 groups, each of which received a different construct. The first group received a traditional Krackow suture repair, the second group was repaired using a jig-assisted percutaneous suture, and the third group received a repair using a jig-assisted percutaneous repair modified with suture anchors placed into the calcaneus. The specimens were tested with cyclical loading and to ultimate failure. Cyclical loading showed a trend toward a stronger repair with the use of suture anchors after 10 cycles (p = .295), 500 cycles (p = .120), and 1000 cycles (p = .040). The ultimate load to failure was greatest in the group repaired with the modified knotless technique using the suture anchors (p = .098). The results of the present study show a clear trend toward a stronger construct in Achilles repair using a knotless suture anchor technique, which might translate to a faster return to activity and be more resistant to an early and aggressive rehabilitation protocol. Further clinical studies are warranted to evaluate this technique in a patient population.     

CORR® ORS Richard A. Brand Award for Outstanding Orthopaedic Research: Engineering Flexor Tendon Repair With Lubricant,Cells, and Cytokines in a Canine Model

Background

Adhesions and poor healing are complications of flexor tendon repair.

Questions/purposes

The purpose of this study was to investigate a tissue engineering approach to improve functional outcomes after flexor tendon repair in a canine model.

Methods

Flexor digitorum profundus tendons were lacerated and repaired in 60 dogs that were followed for 10, 21, or 42 days. One randomly selected repair from either the second or fifth digit in one paw in each dog was treated with carbodiimide-derivatized hyaluronic acid, gelatin, and lubricin plus autologous bone marrow stromal cells stimulated with growth and differentiation factor 5; control repair tendons were not treated. Digits were analyzed by adhesion score, work of flexion, tendon-pulley friction, failure force, and histology.

Results

In the control group, 35 of 52 control tendons had adhesions, whereas 19 of 49 treated tendons had adhesions. The number of repaired tendons with adhesions in the control group was greater than the number in the treated group at all three times (p = 0.005). The normalized work of flexion in treated tendons was 0.28 (± 0.08), 0.29 (± 0.19), and 0.32 (± 0.22) N/mm/° at Day 10, Day 21, and Day 42 respectively, compared with the untreated tendons of 0.46 (± 0.19) at Day 10 (effect size, 1.5; p = 0.01), 0.77 (± 0.49) at Day 21 (effect size, 1.4; p < 0.001), and 1.17 (± 0.82) N/mm/° at Day 42 (effect size, 1.6; p < 0.001). The friction data were comparable to the work of flexion data at all times. The repaired tendon failure force in the untreated group at 42 days was 70.2 N (± 8.77), which was greater than the treated tendons 44.7 N (± 8.53) (effect size, 1.9; p < 0.001). Histologically, treated repairs had a smooth surface with intrinsic healing, whereas control repairs had surface adhesions and extrinsic healing.

Conclusions

Our study provides evidence that tissue engineering coupled with restoration of tendon gliding can improve the quality of tendon healing in a large animal in vivo model.

Clinical Relevance

Tissue engineering may enhance intrinsic tendon healing and thus improve the functional outcomes of flexor tendon repair.     

Timing matters: NSAIDs interfere with the late proliferation stage of a repaired rotator cuff tendon healing in rats

Introduction

Rotator cuff (RC) tear is a common problem that causes pain and can limit shoulder function. Non-steroidal anti-inflammatory drugs (NSAIDs) are often prescribed for musculoskeletal pain, including the pain subsequent to RC repair. NSAIDs have been reported to affect bone metabolism and fracture healing^, but there is little evidence about their effect on tendon healing. We investigated the effect of meloxicam (non-steroidal anti-inflammatory drug) on the healing of RC tendons when given immediately after surgical repair.

Materials and methods

Thirty-nine rats underwent acute RC tear and repair. Group A (n = 13) received daily intraperitoneal (IP) injections of meloxicam for the first 10 postoperative days. Group B (n = 13) received IP injections of meloxicam starting from postoperative day 11. Group C (n = 13, controls) received daily IP injections of saline for 3 weeks. The animals were killed 3 weeks after surgery and the RC was evaluated by gross inspection, biomechanical testing and histological examination.

Results

Group B displayed a significantly lower mean maximal load at 3 weeks than group C (P = 0.02) and group A (P = 0.05). Stiffness was significantly lower in B group as compared to A group (P = 0.05). Qualitative examination of histology specimens did not disclose any apparent differences with respect to cellularity, vascularity, healing, and collagen orientation.

Conclusions

We conclude that meloxicam decreases the biomechanical strength of repaired rat RCs when administered between 11 and 20 days after the repair.     

A biomechanical comparison between locked 3.5-mm plates and 4.5-mm plates for the treatment of simple bicondylar tibial plateau fractures: is bigger necessarily better?

Background

Evolution of periarticular implant technology has led to stiffer, more stable fixation constructs. However, as plate options increase, comparisons between different sized constructs have not been performed. The purpose of this study is to biomechanically assess any significant differences between 3.5- and 4.5-mm locked tibial plateau plates in a simple bicondylar fracture model.

Materials and methods

A total of 24 synthetic composite bone models (12 Schatzker V and 12 Schatzker VI) specimens were tested. In each group, six specimens were fixed with a 3.5-mm locked proximal tibia plate and six specimens were fixed with a 4.5-mm locking plate. Testing measures included axial ramp loading to 500 N, cyclic loading to 10,000 cycles and axial load to failure.

Results

In the Schatzker V comparison model, there were no significant differences in inferior displacement or plastic deformation after 10, 100, 1,000 and 10,000 cycles. In regards to axial load, the 4.5-mm plate exhibited a significantly higher load to failure (P = 0.05). In the Schatzker VI comparison model, there were significant differences in inferior displacement or elastic deformation after 10, 100, 1,000, and 10,000 cycles. In regards to axial load, the 4.5-mm plate again exhibited a higher load to failure, but this was not statistically significant (P = 0.21).

Conclusions

In the advent of technological advancement, periarticular locking plate technology has offered an invaluable option in treating bicondylar tibial plateau fractures. Comparing the biomechanical properties of 3.5- and 4.5-mm locking plates yielded no significant differences in cyclic loading, even in regards to elastic and plastic deformation. Not surprisingly, the 4.5-mm plate was more robust in axial load to failure, but only in the Schatzker V model. In our testing construct, overall, without significant differences, the smaller, lower-profile 3.5-mm plate seems to be a biomechanically sound option in the reconstruction of bicondylar plateau fractures.     

Weak link of tendon–bone healing and a control experiment to promote healing

Objective

This study aims to observe the mechanical weak point and histological features of tendon–bone interface after anterior cruciate ligament reconstructive surgery and to explore the tendon–bone healing effects of the platelet-rich gel (PRG) + deproteinized bone (DPB) compound.

Methods

A total of 48 New Zealand white rabbits were randomly divided into normal group, model (without embedding), experimental (embedded with the PRG + DPB compound), and control (embedded with DPB) groups. The rabbits were executed at 2, 4, 8, and 12 weeks after the operation. Then, micro-computed tomography scan and uniaxial tensile test were conducted. The fractured specimens were subjected to histological observation.

Results

At 4, 8, and 12 weeks after the operation, the bone density of the tendon–bone bound section of the experimental group was higher than that of the other groups (P < 0.05). At 4 and 8 weeks, the maximum tensile load of the experimental group was obviously higher than that of the control and model groups (P < 0.05). Histological observation indicated that the tendon–bone interface in the experimental group had more cartilage and bone tissue growing toward the internal tendon, but the fracture layer mainly occurred in the non-ankylosed part.

Conclusion

The mechanical weak point of the early tendon–bone interface was in the immature fibrous tissue. The PRG + DPB compound can effectively trigger tendon–bone healing by promoting the maturation and ossification of the tendon–bone tissue. This compound improved the tensile strength of the healing interface and reduced bone tunnel enlargement.     

Suture bridge transosseous equivalent repair is stronger than transosseous tied braided-tape

Background

This study biomechanically compares two methods of supraspinatus repair: single row transosseous braided-tape (BT) and suture bridge transosseous equivalent (SBTE) with 2 medial anchors and 2 lateral anchors. The purpose is to test the hypothesis that BT provides superior or equal biomechanical strength compared to SBTE.

Results of operative treatment for recalcitrant retrocalcaneal bursitis and midportion Achilles tendinopathy in athletes

Background

The results of operative treatment for recalcitrant midportion Achilles tendinopathy and recalcitrant retrocalcaneal bursitis were evaluated using the patient administered, disease specific, and validated VISA-A-G questionnaire.

Methods

A cohort of 89 patients was prospectively followed. These patients underwent operations for sport induced midportion Achilles tendinopathy (39 procedures) or retrocalcaneal bursitis (55 procedures). Depending on the individual intraoperative findings the patients of either disease were treated with two respective operative modifications (tendon repair or no tendon repair). Preoperative and follow-up status (3, 6, and 12 months) were investigated using the VISA-A-G questionnaire.

Results

Preoperatively, the four groups scored from 37.0 ± 17.6 to 45.9 ± 15.2 (p = 0.376–0.993) on the VISA-A-G questionnaire. Six and 12 months postoperatively, the VISA-A-G scores improved significantly (p < 0.001). Twelve months postoperatively, the groups’ scores were not different (p = 0.100–0.952) and ranged from 80.8 ± 17.9 to 90.3 ± 10.6.

Conclusion

Retrocalcaneal bursitis and midportion Achilles tendinopathy responded equally well to operative treatment. When repaired, additional tendon lesions did not influence this result. We demand to differentiate not only between midportion Achilles tendinopathy and retrocalcaneal bursitis but also to identify additional Achilles tendon lesions to specifically address these lesions during operative procedures.

Level of evidence

Prospective mixed cohort study.     

The fate and role of bone graft-derived cells after autologous tendon and bone transplantation into the bone tunnel

Background

Grafting bone between the tendon graft and the bone tunnel in anterior cruciate ligament reconstruction increases the mechanical strength of the tendon graft. However, the biological role of the bone graft is unclear. The purpose of this research was to elucidate the role of bone graft cells after autologous tendon graft into the bone tunnel with an autologous bone graft in green fluorescent protein (GFP) transgenic rats.

Methods

The Achilles tendons of Sprague-Dawley (SD) wild-type rats and bone of GFP rats were harvested and transplanted into bone tunnels drilled in the femurs at the knees of SD rats. The femurs were harvested at 1, 2, and 4 weeks after transplantation and histologically investigated using hematoxylin and eosin staining and immunostaining of heat shock protein 47 (HSP47), macrophages, and type I and type III collagens. Biomechanical tests were performed on the tendon graft 2 and 4 weeks after transplantation to evaluate the ultimate force to failure.

Results

A small number of GFP-positive cells was seen in the tendon graft 2 weeks after transplantation. The cell count in the tendon graft was increased at 4 weeks after transplantation. HSP47-positive cells and macrophage-stained cells present in the tendon graft corresponded with the GFP-positive cells. By 2 weeks after transplantation, the relative areas of immunostained type I and III collagens in the tendon graft had declined significantly in the bone graft group compared to the control. The ultimate failure load in the bone graft group was higher than that in the control group at both 2 and 4 weeks after transplantation.

Conclusions

This research showed that, within 4 weeks of transplantation, bone graft cells migrate to the tendon graft, where they differentiate into cells involved in collagen production and macrophages. Bone graft cells may contribute to the early stage remodeling of tendon grafts.     

Suture anchor tenodesis in repair of distal Achilles tendon injuries

Background

Distal Achilles tendon avulsions are in the form of either bony and nonbony avulsion of Achilles tendon from its calcaneal insertion.

Methods

Four patients with distal Achilles tendon avulsions or ruptures which were treated with tendon to bone repair using suture anchors are presented here. Operated leg was immobilized in above-knee cast for 4 weeks while the patient walked non-weight-bearing. Then, cast was changed to below knee, and full weight-bearing was allowed. Patients underwent gait analysis minimum at first postoperative year.

Results

Mean American Orthopedics Foot Ankle Society ankle/hindfoot score of patients at last visit was 88.75 (range 85–100), and Achilles tendon total rupture score was 77.75 (range 58–87). Mean passive dorsiflexion of injured ankles (14° ± 5°) was lower than uninjured ankles (23° ± 9°). All the kinematic parameters of gait analysis were comparable to the uninjured side. Maximum plantar flexion power of injured ankle was 1.40 W/kg, and this was significantly lower than the contralateral side value 2.38 W/kg; (P = 0.0143).

Conclusions

There were no visually altered gait or problems in daily life. Suture anchor tenodesis technique of distal Achilles tendon avulsions was successful in achieving durable osteotendinous repairs.     

Relative Fixation Strength of Rabbit Subscapularis Repair Is Comparable to Human Supraspinatus Repair at Time 0

Background

Recent evidence suggests that the rabbit subscapularis tendon may be anatomically, biomechanically, and histologically suitable to study rotator cuff pathology and repair. However, biomechanical comparisons of rotator cuff repairs in this model have not been evaluated and compared to those in human cadaveric specimens.

Questions/purposes

We quantified the biomechanical properties of the repaired rabbit subscapularis tendon after (1) single-row, (2) double-row, and (3) transosseous-equivalent rotator cuff repair techniques and compared the ratios of repairs to previously published data for human repairs.

Methods

Tensile testing was performed on 21 New Zealand White rabbit subscapularis tendon-humerus complexes for single-row repair, double-row repair, and transosseous-equivalent repair (n = 7 for each group). Video digitizing software was used to quantify deformation. Load elongation data were then used to quantify structural properties. We compared the ratios of rotator cuff repairs for the rabbit data to data from human supraspinatus repair studies previously performed in our laboratory. For our primary end points (linear stiffness, yield load, ultimate load, and energy absorbed to failure), with the numbers available, our statistical power to detect a clinically important difference (defined as 15%) was 85%.

Results

The ratios of single-row/double-row repair were 0.72, 0.73, 0.71, and 0.66 for human supraspinatus and 0.77, 0.74, 0.79, and 0.89 for rabbit subscapularis repair for linear stiffness, yield load, ultimate load, and energy absorbed to failure, respectively. The ratios of double-row/transosseous-equivalent repair were 1.0, 0.86, 0.70, and 0.41 for human supraspinatus and 1.22, 0.85, 0.76, and 0.60 for rabbit subscapularis for linear stiffness, yield load, ultimate load, and energy absorbed to failure, respectively. There were no differences comparing rabbit to human repair ratios for any parameter (p > 0.09 for all comparisons).

Conclusions

Subscapularis repairs in the rabbit at Time 0 result in comparable ratios to human supraspinatus repairs.

Clinical Relevance

The biomechanical similarities between the different types of rotator cuff repair in the rabbit subscapularis and human supraspinatus at Time 0 provide more evidence that the rabbit subscapularis may be an appropriate model to study rotator cuff repairs.     

Arthroscopic posterior cruciate ligament reconstruction by using hamstring tendon autograft and transosseous screw fixation: minimal 3 years follow-up

Background

The aim of this trial is to prospectively evaluate the outcomes of PCL reconstruction by means of quadruple hamstring tendon autograft with a double-fixation method at minimal 3-year follow-up.

Materials and methods

Only patients who underwent PCL reconstruction without any other concomitant injury were included in this study. A hamstring tendon graft is composed of a quadruple-stranded gracilis tendon and semitendinosus tendon about 10 cm in length. An arthroscopic technique via a two incision and a double-fixation method was applied. Clinical evaluations were performed for 52 patients. Clinical assessment of patients included the Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, thigh muscle evaluation, and radiographic investigation.

Results

On the Lysholm knee score, 90 % of the patients displayed good or excellent rating in the final assessment. In the IKDC rating analyses, 60 % of the patients demonstrated 3–5-mm ligament laxity. For the IKDC final rating, 81 % were normal or nearly normal. Seventy-nine percent of the cases revealed less than a 10-mm difference in thigh girth between their reconstructed and contra lateral limbs.

Conclusion

Arthroscopic PCL reconstruction using quadruple hamstring tendon autograft provides acceptable outcomes at a minimum 3-year follow-up. The four-stranded hamstring tendon graft is suitable in graft size and results in minimal harvesting morbidity. We recommend that quadruple hamstring tendon graft be chosen for PCL reconstruction to achieve good ligament reconstruction. A double-fixation method which has been applied in this trial can be used to provide rigid fixation.     

The biomechanical characteristics of arthroscopic tibial inlay techniques for posterior cruciate ligament reconstruction: in vitro comparison of tibial graft tunnel placement

Purpose

The hypothesis of the present study was that the biomechanical properties of arthroscopic tibial inlay procedures depend on tibial graft bone block position.

Methods

Five paired fresh-frozen human cadaveric knee specimens were randomized to a reconstruction with quadriceps tendon placing the replicated footprint either to the more proximal margin of the remnants of the anatomical PCL fibrous attachments (group A) or to the distal margin of the anatomical PCL fibrous attachments at the edge of the posterior tibial facet to the posterior tibial cortex in level with the previous physis line (group B). The relative graft-tibia motions, post cycling pull-out failure load and failure properties of the tibia-graft fixation were measured. Cyclic displacement at 5, 500 and 1,000 cycles, stiffness and yield strength were calculated.

Results

The cyclic displacement at 5, 500 and 1,000 cycles measured consistently more in group A without statistically significant difference (4.11?±?1.37, 7.73?±?2.73 and 8.18?±?2.75 mm versus 2.81?±?1.33, 6.01?±?2.37 and 6.46?±?2.37 mm). Mean ultimate load to failure (564.6?±?212.3) and yield strength (500.2?±?185.9 N) were significantly higher in group B (p?Conclusion Replicating the anatomical PCL footprint at the posterior edge of the posterior tibial facet yields higher pull-out strength and less cycling loading displacement compared to a tunnel position at the centre of the posterior tibial facet.     

Biomechanical strain characteristics of soft tissue biceps tenodesis and bony tenodesis

Background

Biomechanical analysis of biceps tenodesis procedures has historically focused on load to failure models. Minimal data exists for the analysis of biomechanical strain properties of the biceps tendon in a sub-failure, physiologic cadaver model.

Hypothesis

Tendon strain characteristics are different between bony and soft tissue tenodesis surgery, and the soft tissue tenodesis procedure reproduces a strain pattern more similar to the native biceps tendon.

Methods

Eight fresh frozen cadaver upper extremities were mounted onto a custom device that controls shoulder abduction and rotation. Strain on the tendon was measured using a differential variable reluctance transducer as the arm was moved through cycles of abduction and external rotation. Each arm was mounted once, and all 3 testing procedures were performed on each of the 8 specimens. Statistical analysis was completed using ANOVA, followed by multiple comparisons with Bonferroni correction.

Results

The bony tenodesis model placed higher strain on the biceps tendon than the soft tissue tenodesis (p = 0.025). Also, the bony tenodesis model increased the strain on the biceps tendon when compared to the native tendon (p = 0.031). In contrast, the soft tissue tenodesis did not significantly alter strain when compared to the native tendon (p = 0.089).

Conclusion

The soft tissue tenodesis procedure better maintained the native strain environment when compared to the bony tenodesis using an interference screw. Due to this closer approximation of native biceps tendon biomechanics, the soft tissue procedure may be more preferable clinically than the bony tenodesis. Level of Evidence: 1, Controlled Laboratory Study.     

Root tear of the meniscus: biomechanical evaluation of an arthroscopic refixation technique

Background

Aim of the current study was to evaluate the structural properties of an arthroscopic refixation technique for meniscal root tears.

Hypothesis

Arthroscopic two suture root tear refixation technique using a transtibial approach restores the structural properties of the intact meniscus attachment more closely than a one suture technique.

Methods

Lateral root tear refixation was performed in a porcine knee model. Using a material testing machine, structural properties were determined after a cyclic loading protocol comparing transtibial tunnel reconstruction using one or a double suture technique. Intact posterior horn served as control group.

Results

Elongation after cyclic testing was significantly lower for intact and two suture technique when compared to single suture technique. Stiffness was significantly higher for intact constructs with a mean of 53.7 (±6.5) N/m and two suture technique with 44.8 (±9.9) N/m when compared to one suture technique with a mean of 37.1 (±5.4) N/m. In elongation and stiffness, no differences were found between intact and two suture technique. Ultimate failure loads were 325.6 (±77) N for the intact, 273.6 (±45.6) N for two suture technique and 149.8 (±24.3) N for the one suture technique. Both reconstruction techniques showed significantly lower ultimate failure load when compared to the intact control.

Conclusion

Structural properties of root tear fixation using a transtibial single suture technique showed significantly higher elongation and lower stiffness and failure load after cyclic loading compared to the intact, whereas a two suture technique showed no difference in elongation and stiffness; however, lower failure load.     

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique

Introduction

The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model.

Materials and methods

Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing.

Results

Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim.

Conclusions

As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.