Intact Achilles Tendon Research Articles

The effects of zinc sulfate mineral supplementation on Achilles tendon healing in rats.

The Achilles tendon is the most commonly injured and ruptured tendon in the body and typically occurs during participation in sports or recreational activities in men between 30 and 50 years of age. Treatment options for Achilles tendon rupture include conservative and surgical approaches. Conservative treatment is associated with a higher risk of rerupture, while surgical treatment carries a risk of wound site complications. Generally, both methods result in a prolonged tendon healing time. Studies are ongoing to identify biomolecules that aid tendon repair. The main objective of our study is to investigate the effects of zinc sulfate (ZnSO4) mineral supplementation on Achilles tendon healing in rats. Forty-eight female Sprague-Dawley rats were divided into four equal groups (C-15, C-30, ZnSO4-15, and ZnSO4-30) after standard Achilles tendon repair surgery. The ZnSO4-15 and ZnSO4-30 groups received an oral zinc sulfate monohydrate solution (50 mg/kg/day) for 15 and 30 days, respectively. The C-15 and C-30 groups were given 1 mL of distilled water per day orally during the experimental periods. Rats were sacrificed on the 15th and 30th day depending on their groups, and the healing of the operated tendons was evaluated using Movin and Bonar histopathologic scoring. For biomechanical analyses, the operated and intact Achilles tendons of all groups were removed, and tensile tests were performed to determine the tensile strength and toughness values for each tendon. Movin and Bonar scores were significantly lower in the ZnSO4-15 group than in the C-15 group and in the ZnSO4-30 group than in the C-30 group (p<0.05). Although we did not find the biomechanical results statistically significant, the intact tendons of the ZnSO4-15 group exhibited higher toughness than those of the C-15 group, and the tensile strength and toughness values of the operated and intact tendons of the ZnSO4-30 group were also higher than those of the C-30 group. Zinc sulfate monohydrate mineral supplementation had histopathologically positive effects on the proliferation and remodeling stages of Achilles tendon healing and may biomechanically benefit both operated and intact tendons.

Reconstruction of Achilles Tendon Skin Defect Using Single-Stage Reverse Sural Artery Island Flap

Wound complications following open repair of a ruptured Achilles tendon are common and require immediate skin cover. This study analyses the use of a reverse sural artery island flap to cover skin defects over an exposed intact Achilles tendon. Thirteen patients with postoperative wound complications over the tendoachilles were operated upon. All wounds were debrided and reconstructed with a single-stage reverse sural artery island flap. Within 5 weeks of flap cover, 12 wounds healed completely, while 1 flap had superficial necrosis at the margin in a diabetic patient. This eventually healed and did not compromise the final result. None of the flaps had venous congestion. In our hands, reconstructing skin defects following wound complications after Achilles tendon repair with islanded reverse sural artery flap is a reliable and safe option. Level of Evidence: Level IV.

Heterotopic mineral deposits in intact rat Achilles tendons are characterized by a unique fiber-like structure

Heterotopic mineralization entails pathological mineral formation inside soft tissues. In human tendons mineralization is often associated with tendinopathies, tendon weakness and pain. In Achilles tendons, mineralization is considered to occur through heterotopic ossification (HO) primarily in response to tendon pathologies. However, refined details regarding HO deposition and microstructure are unknown. In this study, we characterize HO in intact rat Achilles tendons through high-resolution phase contrast enhanced synchrotron X-ray tomography. Furthermore, we test the potential of studying local tissue injury by needling intact Achilles tendons and the relation between tissue microdamage and HO. The results show that HO occurs in all intact Achilles tendons at 16 weeks of age. HO deposits are characterized by an elongated ellipsoidal shape and by a fiber-like internal structure which suggests that some collagen fibers have mineralized. The data indicates that deposition along fibers initiates in the pericellular area, and propagates into the intercellular area. Within HO deposits cells are larger and more rounded compared to tenocytes between unmineralized fibers, which are fewer and elongated. The results also indicate that multiple HO deposits may merge into bigger structures with time by accession along unmineralized fibers. Furthermore, the presence of unmineralized regions within the deposits may indicate that HOs are not only growing, but mineral resorption may also occur. Additionally, phase contrast synchrotron X-ray tomography allowed to distinguish microdamage at the fiber level in response to needling. The needle injury protocol could in the future enable to elucidate the relation between local inflammation, microdamage, and HO deposition.

Impact of elevated serum advanced glycation end products and exercise on intact and injured murine tendons

ABSTRACT Overview: Delayed tendon healing is a significant clinical challenge for those with diabetes. We explored the role of advanced glycation end-products (AGEs), a protein modification present at elevated levels in serum of individuals with diabetes, on injured and intact tendons using a mouse model. Cell proliferation following tissue injury is a vital component of healing. Based on our previous work demonstrating that AGEs limit cell proliferation, we proposed that AGEs are responsible for the delayed healing process commonly observed in diabetic patients. Further, in pursuit of interventional strategies, we suggested that moderate treadmill exercise may support a healing environment in the presence of AGEs as exercise has been shown to stimulate cell proliferation in tendon tissue. Materials and Methods: Mice began receiving daily intraperitoneal injections of bovine serum albumin (BSA)-Control or AGE-BSA injections (200μg/ml) at 16-weeks of age. A tendon injury was created in the central third of both patellar tendons. Animals assigned to an exercise group began a moderate treadmill protocol one week following injury. The intact Achilles tendon and soleus muscle were also evaluated to assess the effect of BSA and AGE-BSA on un-injured muscle and tendon. Results: We demonstrate that our injection dosing and schedule lead to an increase in serum AGEs. Our findings imply that AGEs indeed modulate gene expression following a patellar tendon injury and have modest effects on gene expression in intact muscle and tendon. Conclusions: While additional biomechanical analysis is warranted, these data suggest that elevated serum AGEs in persons with diabetes may impact tendon health.

Экспериментальное обоснование армирования ахиллова сухожилия новыми способами

the effectiveness of new methods of the Achilles tendon reinforcement. Material and methods The experimental part of the work was performed in 3 stages using 60 biomannikins with intact Achilles tendon. A Krakow suture was used at stage 1 for a group of 20 tendons and a force that would result in rupture of the tendon was measured. Reinforcement was performed using the plantaris tendon (technical innovation offered at the Samara State Medical University) at the 2nd stage and the force required for the appearance of signs of rupture was subsequently measured. A portion of the peroneus longus tendon (RF patent No. 2616767) was used for reinforcement at the 3rd stage and the force measurement produced. Results The mean force required to rupture the Krakow suture applied to the tendon at the first stage was 11.5 kg., The force required to rupture the suture reinforced with the plantaris tendon at the second stage measured 33.4 kg. The force required to rupture the suture reinforced with a portion of the peroneus longus tendon at the third stage was 37.3 kg. Conclusion The new techniques offered to reinforce the Achilles tendon with the plantaris tendon and a portion of the peroneus longus tendon at the distal base facilitated increase in the strength of the injury site by 195.6 % and 214.4 %, respectively.

“Snake Sign” Secondary Sign of Achilles Tendon Rupture

Objective: We describe a secondary sign (Snake sign) due to lax plantar fascia in full-thickness rupture of Achilles tendon. Materials and Methods: A 100 consecutive magnetic resonance images with intact Achilles tendon and second group of 17 patients with Achilles tendon rupture (ATR) were analyzed for Snake sign and angle between the achilles tendon and plantar fascia (APA) was calculated. Results: Significant decrease in the APA (P &lt; 0.0001) with ATR and Snake sign was present in 8 of the 17 cases in the second cohort. Conclusion: Snake sign and APA are useful secondary signs for ATR.

The Effects of Corticosteroid Injection in the Healthy and Damaged Achilles Tendon Model: Histopathological and Biomechanical Experimental Study in Rats.

To show the effects of corticosteroids on inflammatory reactions in the injured Achilles tendon in rats. Thirty-two adult Wistar Albino rats were used in the study. The rats were divided into 4 groups. In the first group (Intact Saline), saline solution was injected to the intact Achilles tendon. In the second group (Intact Corticosteroid), corticosteroid was injected to the intact tendon. In the third group (Injured Saline), saline solution was injected to the injured Achilles tendon. In the fourth group (Injured Corticosteroid), corticosteroid was injected to the injured tendon. All groups were sacrificed on day 30 and Achilles tendons were taken and prepared for histological and biomechanical evaluation. According to the biomechanical test; mean load-to-failure of the Intact Saline group was significantly lower than the Intact Corticosteroid (p=0.016), Injured Saline (p=0.001) and Injured Corticosteroid) (p=0.012) groups. According to the histopathological evaluation, tenocyte mean of the Intact Saline group was statistically lower than the Injured Saline and Injured Corticosteroid groups. Tenocyte mean of the Intact Corticosteroid group was statistically significantly lower than the Injured Saline and Injured Corticosteroid groups. The ground substance mean of the Intact Saline group was significantly lower than the Injured Saline and Injured Corticosteroid groups. The ground substance mean of the Intact Corticosteroid group was significantly lower than the Injured Saline and Injured Corticosteroid groups. There was no statistically significant difference between the groups in terms of calcification. It has been found that there is biomechanical and histopathological significant benefit of intra-tendon corticosteroid administration in the experimentally generated Achilles tendon injury model.

Time-Dependent Alterations of MMPs, TIMPs and Tendon Structure in Human Achilles Tendons after Acute Rupture.

A balance between matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) is required to maintain tendon homeostasis. Variation in this balance over time might impact on the success of tendon healing. This study aimed to analyze structural changes and the expression profile of MMPs and TIMPs in human Achilles tendons at different time-points after rupture. Biopsies from 37 patients with acute Achilles tendon rupture were taken at surgery and grouped according to time after rupture: early (2–4 days), middle (5–6 days), and late (≥7 days), and intact Achilles tendons served as control. The histological score increased from the early to the late time-point after rupture, indicating the progression towards a more degenerative status. In comparison to intact tendons, qRT-PCR analysis revealed a significantly increased expression of MMP-1, -2, -13, TIMP-1, COL1A1, and COL3A1 in ruptured tendons, whereas TIMP-3 decreased. Comparing the changes over time post rupture, the expression of MMP-9, -13, and COL1A1 significantly increased, whereas MMP-3 and -10 expression decreased. TIMP expression was not significantly altered over time. MMP staining by immunohistochemistry was positive in the ruptured tendons exemplarily analyzed from early and late time-points. The study demonstrates a pivotal contribution of all investigated MMPs and TIMP-1, but a minor role of TIMP-2, -3, and -4, in the early human tendon healing process.

Increased mast cell degranulation and co-localization of mast cells with the NMDA receptor-1 during healing after Achilles tendon rupture

The role of inflammation and the mechanism of tendon healing after rupture has historically been a matter of controversy. The purpose of the present study is to investigate the role of mast cells and their relation to the NMDA receptor-1 (a glutamate receptor) during healing after Achilles tendon rupture. Eight female Sprague Dawley rats had their right Achilles tendon transected. Three weeks after rupture, histological quantification of mast cell numbers and their state of degranulation was assessed by histochemistry. Co-localization of mast cell tryptase (a mast cell marker) and NMDA receptor-1 was determined by immunofluorescence. The intact left Achilles tendon was used as control. An increased number of mast cells and a higher proportion of degranulated mast cells were found in the healing Achilles tendon compared to the intact. In addition, increased co-localization of mast cell tryptase and NMDA receptor-1 was seen in the areas of myotendinous junction, mid-tendon proper and bone tendon junction of the healing versus the intact tendon. These findings introduce a possible role for mast cells in the healing phase after Achilles tendon rupture.

A simple suture-guiding device for minimally invasive Achilles tendon repair.

Our hypothesis is to utilize a simple suture-guiding device for minimally invasive repair of Achilles tendon without any extra cost with a minimal risk of rerupture. The purpose of this study is to investigate the results of our minimally invasive technique for Achilles tendon repair using a simple ovarian clamp for suture guiding. Twenty patients with acute Achilles tendon rupture were treated with minimally invasive repair by an expert orthopaedic surgeon. Instead of an Achillon device, an ovarian clamp was directed to the proximal and distal parts of the Achilles tendon. All data relating to daily activities, walking, climbing stairs, sports activity, American Orthopaedic Foot and Ankle Society (AOFAS) and Thermannscores were recorded. Sural nerve was evaluated with physical examination for paraesthesia, hyperaesthesia, lateralis cruris and foot pain in all patient controls. The average AOFAS score was 97.06 (76-100). All patients had intact Achilles tendon at last control. No rerupture was observed. Average time taken to return to work was 30.8 days (28-60 days). After 6 months, all patients returned to their previous sports activities. For Achilles tendon ruptures, minimally invasive repair techniques have shown successful results with low complication rates. Besides their success, some suture-guiding devices bring extra costs for patients or health insurance. Minimally invasive techniques may be performed with devices without any extra cost. Our new suture-guiding device provides knot placement under paratenon like Achillon device to improve outcomes, provides early return to work and minimizes the complications. Finally, our suture-guiding device has no extra cost.

The Effect of Suture Caliber and Number of Core Strands on Repair of Acute Achilles Ruptures

Category: Sports Introduction/Purpose: Controversy exists in Achilles rupture management with options ranging from nonoperative care to open surgical repair. Current literature suggests re-rupture rates are lower with operative repair; therefore, surgery is recommended for active populations. The effect of suture caliber or number of core stands has not been studied in Achilles repair. Varying these factors may allow for a construct capable of earlier weight-bearing and rehabilitation. We hypothesized the number of core strands and suture caliber used in Achilles repair would significantly affect strength and gapping during a simulated early rehabilitation protocol. Methods: Sixteen cadaveric human foot and ankle specimens with no prior injuries or surgeries were utilized. Simulated midsubstance Achilles ruptures were created 6 cm proximal to the calcaneal insertion in 13 ankles. Specimens were randomly allocated to 1 of 4 groups: (1) intact Achilles tendon, (2) open repair using No. 2 suture with four core sutures and two 2mm suture-tape core sutures, (3) open repair using No. 2 suture with two core sutures and four 2mm suture-tape core sutures, and (4) open repair using No. 2-0 suture with 12 core sutures. Repairs consisted of three modified Kessler sutures and an epitenon stitch with a 3-0 monofilament suture. Specimens were subjected to a cyclic loading protocol simulating early, progressive postoperative rehabilitation: 250 cycles at 1 Hz for each loading range: 20-100, 20-200, 20-300, and 20-400 N. A 1-way ANOVA was used to test significance among repair groups. Results: During biomechanical testing, all repairs survived the first two loading stages. However, elongation trends during stage 1 (Figure 1) were consistent among subsequent cyclic loading stages. No significant elongation differences were observed between any of the repair groups (Groups 2-4), with mean displacements of 4.94 ± 0.90 mm, 3.93 ± 0.92 mm, and 5.35 ± 0.34 mm, respectively, at the end of the first loading stage. In Group 2, one repair failed during the fourth stage and 4 survived all four stages. In Group 3, one repair failed during the third stage and two repairs during the fourth stage. In Group 4, two repairs failed during the fourth stage and two survived all four stages. The average number of cycles to failure for Groups 2-4 was 967, 783, and 940 cycles, respectively. Conclusion: In this study, all but one repair survived 750 cycles. This was superior to a 6 core strand repair with No. 2 suture similarly evaluated in a previous study (427 cycles). When 4 of 6 strands were substituted with suture-tape, repair gapping decreased initially; yet, these repairs failed earlier. Gapping in Groups 2 and 4 was similar to the previously evaluated repair; however, the number of cycles to failure was higher. Therefore, substituting suture-tape for 2 core strands or doubling the core strands with a smaller caliber suture may be biomechanically superior and allow for earlier return to function.

Low-Magnitude, High-Frequency Vibration Fails to Accelerate Ligament Healing but Stimulates Collagen Synthesis in the Achilles Tendon.

Background:Low-magnitude, high-frequency vibration accelerates fracture and wound healing and prevents disuse atrophy in musculoskeletal tissues.Purpose:To investigate the role of low-magnitude, high-frequency vibration as a treatment to accelerate healing of an acute ligament injury and to examine gene expression in the intact Achilles tendon of the injured limb after low-magnitude, high-frequency vibration.Study Design:Controlled laboratory study.Methods:Complete surgical transection of the medial collateral ligament (MCL) was performed in 32 Sprague-Dawley rats, divided into control and low-magnitude, high-frequency vibration groups. Low-magnitude, high-frequency vibration started on postoperative day 2, and rats received vibration for 30 minutes a day for 12 days. All rats were sacrificed 2 weeks after the operation, and their intact and injured MCLs were biomechanically tested or used for histological analysis. Intact Achilles tendons from the injured limb were evaluated for differences in gene expression.Results:Mechanical testing revealed no differences in the ultimate tensile load or the structural stiffness between the control and vibration groups for either the injured or intact MCL. Vibration exposure increased gene expression of collagen 1 alpha (3-fold), interleukin 6 (7-fold), cyclooxygenase 2 (5-fold), and bone morphogenetic protein 12 (4-fold) in the intact Achilles tendon when compared with control tendons (P < .05).Conclusion:While no differences were observed in the mechanical or histological properties of the fully transected MCL after low-magnitude, high-frequency vibration treatment, significant enhancements in gene expression were observed in the intact Achilles tendon. These included collagen, several inflammatory cytokines, and growth factors critical for tendons.Clinical Relevance:As low-magnitude, high-frequency vibration had no negative effects on ligament healing, vibration therapy may be a useful tool to accelerate healing of other tissues (bone) in multitrauma injuries without inhibiting ligament healing. Additionally, the enhanced gene expression in response to low-magnitude, high-frequency vibration in the intact Achilles tendon suggests the need to further study its potential to accelerate tendon healing in partial injury or repair models.

Detection of slow-cycling and stem/progenitor cells in different regions of rat Achilles tendon: response to treadmill exercise

Tendons generally exhibit poor healing capacity, probably due to slow cell regeneration potential and low vascularization. The potential to regenerate may partly be due to activation of stem/progenitor cells localized in the tendon or its vicinity. In the present study, we attempted to determine where in the rat Achilles tendon stem/progenitor cells reside and to investigate the effect of exercise on cell proliferation in the in vivo situation. We used bromodeoxyuridine (BrdU) labelling to investigate proliferation and label-retaining cells (i.e. slow-cycling cells) in non-exercised and exercised rats, in combination with immunostaining of the stem cell marker nucleostemin. Rat Achilles tendons were harvested 14, 28, 56 and 105 days after BrdU administration. We found the proportion of stem/progenitor cells to be twice as high in the distal tendon (DT) compared with the mid/proximal tendon (MPT) and that paratenon/endotenon regions appear to host a pool of existing stem/progenitor cells. Exercise increased the BrdU-stained cell population after 14 days only (DT region p = 0.032, MPT p = 0.065), indicating effect mainly on more differentiated cells, since the nucleostemin-positive cells (i.e. stem/progenitor cells) remained unaffected in the intact Achilles tendon. Stem/progenitor cells exist in several areas of the rat Achilles tendon which implies a possible stem cell regeneration pool of different origins. The distal region has twice the amount of stem/progenitor cells compared with the mid/proximal region, indicating a potentially higher stem cell activity in this tissue. Daily moderate exercise (treadmill running) mainly improves in vivo cell proliferation in rapidly proliferating cells, whereas the stem/progenitor pool remains constant.

Metabolic activity in early tendon repair can be enhanced by intermittent pneumatic compression

Since Achilles tendon healing is protracted, more knowledge of metabolites known to meet the demands for biosynthesis and proliferation is needed. We hypothesized that essential metabolites, glutamate, glucose, lactate, pyruvate and glycerol, are present and upregulated in healing Achilles tendons. We moreover hypothesized that adjuvant intermittent pneumatic compression (IPC), which increases blood flow, upregulates metabolite concentrations. Twenty patients with acute Achilles tendon rupture were recruited, operated, and included. The control group, 15 patients, received plaster cast immobilization, while five patients received adjuvant foot IPC beneath the plaster cast. At 2 weeks postoperatively, microdialysis of the healing and contralateral intact Achilles tendons was followed by quantification of metabolites. Healing compared to intact tendons of the controls exhibited significantly increased concentrations (mM) of glutamate (60 ± 14 vs 20 ± 11), lactate (1.15 ± 0.60 vs 0.64 ± 0.35), and pyruvate (81 ± 29 vs 35 ± 25, μM). Healing tendons of the IPC vs control group displayed higher levels of glutamate (84 ± 15 vs 62 ± 16) and glucose (3.44 ± 0.62 vs 2.62 ± 0.72); (P < 0.05) and trends toward higher concentrations of pyruvate, lactate, and glycerol (P < 0.10). The present study demonstrates that early Achilles tendon repair entails and upregulates local essential metabolites. This metabolic response can, during tendon healing with plaster cast immobilization, be promoted by adjuvant IPC.

Preparation and characterization of decellularized tendon slices for tendon tissue engineering

To develop a naturally derived tendon tissue engineering scaffold with the preservation of the native ultrastructure, tensile strength, and biochemical composition of the tendon extracellular matrix (ECM), decellularized tendon slices (DTSs) were prepared using repetitive freeze/thaw of the intact Achilles tendons, frozen section, and nuclease treatment. The DTSs were characterized in the native ultrastructure, mechanical properties, biochemical composition, and cytocompatibility. Histological examination and DNA quantification analysis confirmed that cells were completely removed from tendon tissue by repetitive freeze/thaw in combination with nuclease treatment 12 h. The intrinsic ultrastructure of tendon tissue was well preserved based on scanning electron microscopy examination. The tensile strength of the DTSs was retained 85.62% of native tendon slice. More than 93% of proteoglycans (fibromodulin, biglycan) and growth factors (TGF-β1, IGF-1, VEGF, and CTGF) inherent in tendon ECM were preserved in the DTSs according to ELISA analysis. Furthermore, the DTSs facilitated attachment and repopulation of NIH-3T3 fibroblasts in vitro. Overall, the DTSs are sheet scaffolds with a combination of elemental mechanical strength and tendon ECM bioactive factors that may have many potential applications in tendon tissue engineering.

A comparison of percutaneous and mini-open techniques of Achilles tenotomy: An experimental study in rats

To investigate the effect of Achilles tenotomy performed percutaneously and by mini-open methods on tendon healing and final strength. In two groups, each consisting of 14 rats, percutaneous and mini-open techniques in Achilles tenotomy were compared in terms of biomechanical, histological and gross properties. In the gross evaluation, it was observed that an obvious thickening and adhesion to the subcutaneous tissue of the healing tendon were observed in nearly all rats in which the mini-open technique was performed. In the biomechanical analysis, there was no significant difference between percutaneous and mini-open groups and between operated and intact Achilles tendons in both groups, in terms of tendon strength (P>0.05). In the histological evaluation, irregularity in the parallel pattern of the collagen fibres, emergence of a non-specific collagenous tissue formation and infiltration of mild mononuclear inflammatory cells were reported. These changes were more marked in the rats in which the percutaneous technique was performed. Mini-open technique for Achilles tenotomy may be considered as an alternative method of treatment to apply the tenotomy technique in a secure way. There are two basic advantages of Achilles tenotomy performed by the mini-incision open technique: (1) a complete tenotomy is guaranteed, as it has to be in the original Ponseti technique, (2) iatrogenic neuro-vascular injury risk is nearly completely avoided due to the subparatenon exploration of the tendon and direct visual observation during the transection. The mini-open technique may only be used in cases in which a vascular compromise is clinically suspected or confirmed by Doppler ultrasonography and/or arteriography. On the other hand, the technique may be performed in all cases routinely by the choice of the surgeon.

The Effect of Ankle Position on the Static Tension in the Achilles Tendon Before and After Operative Repair: A Biomechanical Cadaver Study

We hypothesized that there no need to position the foot in plantarflexion after operative repair of an Achilles tendon rupture. In five fresh cadaver lower extremity specimens, the static tension in the Achilles tendon was measured as the ankle was sequentially dorsiflexed from 30, to 20, to 10, to 0 degrees of plantarflexion. The tendon was then transected and repaired using a modified Krakow locking loop suture technique. The tension in the tendon was again measured as the foot was sequentially dorsiflexed through the same range of motion: 30, to 20, to 10, to 0 degrees. The repair was then tensile tested to failure. The intact Achilles tendons generated on average 10 N, 10 N, 15.8 N and 31.9.0 N of tension at 30, 20, 10, and 0 degrees of plantarflexion, respectively. After a modified Krakow locking loop repair, the tension across the repair site was 10 N, 11.46 N, 18.4 N, and 30.3 N at 30, 20, 10, and 0 degrees of plantarflexion. Thus, moving the ankle from 30 degrees to neutral placed an additional force of 21.9 N on the intact tendon and 20.3 N on the repaired tendon. The mean tensile strength of the modified Krakow repair was 598.6 N (range 167 1129 N). The tension in the repaired tendon at neutral position is only a small percentage (6.4%) of the strength of the tendon when operatively repaired by a modified Krakow locking loop suture technique. Our results suggest that the ankle joint does not have to be positioned in plantarflexion after operative repair using the described technique.

A clinical test to avoid sural nerve injuries in percutaneous Achilles tendon repairs

Percutaneous repairs of Achilles tendon ruptures has gained popularity due the reduced incidence of wound complications, however its use is still limited by the high incidence of sural nerve injuries associated with these repairs. The only technique described to avoid this adverse event is to surgically expose the nerve peri-operatively. In our study, we describe and validate a clinical technique to identify the sural nerve. The sural nerve was mapped using this technique both clinically and by Ultrasound (US) in a cohort of male subjects with intact Achilles tendons. We demonstrated an excellent correlation between the clinical and US mapping. This study demonstrates an accurate and repeatable clinical technique for mapping the sural nerve in conjunction with percutaneous Achilles tendon repairs.

Evaluation of collagen fiber maturation and ordering in regenerating tendons employing H-1 double quantum filtered NMR spectroscopy

It is difficult to monitor the chronic stage of the healing process of ruptured tendons employing the present diagnostic modes. However, the results of this study have shown that 1H double quantum filtered (DQF) NMR spectroscopy is sensitive to the later stages of the healing process. Regenerated tendons of rabbits were dissected and measured at the end of the acute phase (three weeks), the subacute phase (nine weeks), and the chronic phase (13 and 18 weeks after tenotomy). Four parameters were determined by 1H DQF NMR spectroscopy: (a) the maximum signal intensity ( h max) relative to the single quantum spectrum, (b) the creation time of the maximum signal intensity ( τ max), (c) the decay time from the maximum signal intensity to a value half of that intensity ( τ 1/2) and (d) the residual dipolar splitting of water ( δ), representing the order of the collagen fibers. The values of h max, τ max, τ 1/2, and δ of the intact Achilles tendons were 11.3±1.0%, 0.48±0.03 ms, 0.67±0.04 ms and 732±62 Hz (mean ± SEM, n=6), respectively. In the regenerating tendon, h max increased from 0.41±0.12% at three weeks to 7.07±0.77% at 18 weeks, τ max decreased from 1.88±0.31 ms at three weeks to 0.72±0.04 ms at 18 weeks, τ 1/2 decreased from 11.6±1.8 ms at 3 weeks to 1.48±0.16 ms at 18 weeks, and δ increased from 129±8 Hz at three weeks to 414±29 Hz at 18 weeks. We have concluded that reordering of collagen fibers proceeds continuously even in the chronic stage of healing. Thus, the 1H DQF NMR spectroscopy is a useful non-invasive technique to evaluate the reconstruction and the order of collagen fibers in regenerating tendon. It is also suggested that τ 1/2 and h max are most useful for in vivo DQF NMR spectroscopy and imaging, respectively, in combination with τ max.

Collagen fibril size and crimp morphology in ruptured and intact Achilles tendons.

The present study examined the hypothesis that collagen fibril diameter and crimp angle in ruptured human Achilles tendons differed from that of intact ones. Tissue samples were obtained from the central core (distal core) and the posterior periphery (distal superficial) at the rupture site, and the proximally intact (proximal superficial) part of the tendon in 10 subjects (38+/-8 years) with a complete tendon rupture. For comparisons corresponding tissue samples were procured from age (38+/-7 years) and gender matched intact Achilles tendons during routine forensic autopsy. The cross-sectional area density and diameter distribution of fibrils were analyzed using stereological techniques of digitized electron microscopy biopsy cross-sections, while crimp angle was measured by the changing banding pattern of collagen fibers when rotated between crossed polars. Nine of 10 persons with tendon ruptures reported that the injury did not occur during exceedingly large forces, and none experienced any symptoms in the days or months prior to the injury. Fibril diameter distribution showed no region-specific differences in either the ruptured or intact tendons for either group. However, in the distal core there were fewer fibrils in the ruptured compared to the intact tendons in 60-150 nm range, P<0.01. Similarly, in the distal superficial portion there were fewer fibrils in the ruptured compared to the intact tendons in the 90-120 nm range, 2P<0.05, while there were no differences in the proximal superficial tendons. Crimp angle did not display any region-specific differences, or any difference between the rupture and intact tendons. In conclusion, these data suggest that although crimp morphology is unchanged there appears to be a site-specific loss of larger fibrils in the core and periphery of the Achilles tendon rupture site. Moreover, the lack of symptoms prior to the rupture suggests that clinical tendinopathy is not an etiological factor in complete tendon ruptures.