Effect of training and sudden detraining on the patellar tendon and its enthesis in rats

Background  

Different conditions may alter tendon characteristics. Clinical evidence suggests that tendon injuries are more frequent in athletes that change type, intensity and duration of training. Aim of the study was the assessment of training and especially detraining on the patellar tendon (PT) and its enthesis.     

Effect of hyperbaric oxygen on the ligament healing process in rats

Animal experiments were done to investigate whether administration of hyperbaric oxygen promotes scar tissue formation, increases expression of the Type I procollagen gene, and improves the tensile properties of healing ligament. In 76 Sprague-Dawley rats, a 2-mm segment of the medial collateral ligament was removed. Thirty-eight rats were exposed to hyperbaric oxygen at 2.5 atmospheres absolute for 2 hours 5 days per week (Group H), whereas the remaining rats were exposed to room air (Group C). The animals were sacrificed at 3, 7, 14, and 28 days postoperatively. In situ hybridization histochemistry was done to examine the Type I procollagen gene expression in healing ligaments in 40 rats, whereas a tensile failure test was done in the remaining rats. The amount of scar tissue was greater in Group H than in Group C. Type I procollagen gene expression at 7 or 14 days was significantly greater in Group H than in Group C. The ultimate load and stiffness in Group H were significantly greater than in Group C at 14 days. Administration of hyperbaric oxygen promotes scar tissue formation and increases Type I procollagen gene expression in healing ligaments. These effects are associated with the improvement of their tensile properties.     

A comparative study of the healing of tendon autograft and tendon-bone autograft using patellar tendon in rabbits

In order to compare the healing of tendon to bone and the healing of bone to bone in a rabbit model, the lateral 4 mm of patellar tendons were detached from their insertion into the tibia either subperiosteally (group I) or with a bone block (group II) and implanted into drill holes in the proximal articular surface of the tibia. The histological and biomechanical features of the graft incorporation were observed at 2, 4, 8 and 12 weeks. Histological patterns similar to normal tendon-bone attachment were seen at the tendon-bone interface in group I by 12 weeks, while direct bony union was seen in group II by 8 weeks. The maximum tensile load and stiffness were significantly greater in group II at 4 and 8 weeks while the difference between the two groups was not significant at 2 and 12 weeks. These findings show that more rapid incorporation of the graft occurs in group II although no significant difference in biomechanical parameters was noted once healing was complete.     

The effect of platelet-rich plasma gel in the early phase of patellar tendon healing

Introduction  

The aim of this study is to assess if an application of platelet-rich plasma (PRP) gel would improve the mechanical properties of rabbit’s patellar tendon after resecting its central portion.     

Magnetic resonance evaluation of remodeling process in patellar tendon graft

Several studies have shown the accuracy of magnetic resonance imaging in evaluating the reconstructed anterior cruciate ligament. The purpose of the current study was to clarify the clinical usefulness of magnetic resonance imaging for evaluating the reconstructed anterior cruciate ligament in comparison with using arthroscopy. Sixty-nine patients who had an anterior cruciate ligament reconstruction using a bone-tendon-bone autograft were examined by magnetic resonance imaging and arthroscopy an average of 12 months after surgery. There were 41 males and 28 females with an average age of 25.9 years (range, 15-66 years). The interval from surgery to the magnetic resonance imaging or arthroscopic evaluation was a mean of 12 months (range, 4-32 months). The magnetic resonance imaging findings of the reconstructed anterior cruciate ligament were classified as either high, intermediate, or low intensity. The arthroscopic findings also were classified as either graft impingement at the intercondylar notch or no impingement. In the 47 anterior cruciate ligament grafts that were not impinged, the signal intensity remained low and did not increase during second-look arthroscopy. In contrast, 22 anterior cruciate ligament grafts that were impinged showed an increased signal intensity in the distal area of the graft at the time of the second-look arthroscopy. Furthermore, no significant correlation was observed between the presence of a high signal intensity and postoperative instability. The high signal intensity of the anterior cruciate ligament graft on magnetic resonance imaging was found to be caused by graft impingement. These findings therefore show a clear association between graft impingement and the subsequent appearance of the graft on magnetic resonance imaging.     

Polydeoxyribonucleotide improves tendon healing following achilles tendon injury in rats

Tendon injuries are major musculoskeletal disorders. Polydeoxyribonucleotide activates the adenosine receptor subtype A2A, resulting in tissue growth and neogenesis. This experimental study confirms that polydeoxyribonucleotide can improve secretion of various growth factors, promote collagen synthesis, and restore tensile strength of the Achilles tendon in a rat model with Achilles tendon injury. Thirty‐six male Sprague‐Dawley rats, aged 7 weeks, were divided into two groups, and the Achilles tendon was transected and repaired using the modified Kessler's method. In the experimental group (n = 18), the rats received daily intraperitoneal administration of polydeoxyribonucleotide (8 mg/kg/day for 1, 2, or 4 weeks). The control groups received the same amount of normal saline. The rats were euthanized at 1, 2, and 4 weeks, and tissues from the repair site were harvested. The cross‐sectional area of the tendon was significantly increased at 2 and 4 weeks in polydeoxyribonucleotide group (p = 0.008 and p = 0.017, respectively). Moreover, tendons in the polydeoxyribonucleotide group were more resistant to mechanical stress at 2 and 4 weeks (p = 0.041 and p = 0.041, respectively). The staining levels of collagen type I in the experimental group were significantly stronger at 2 and 4 weeks (p = 0.026 and p = 0.009, respectively). Furthermore, higher expression levels of fibroblast growth factor, vascular endothelial growth factor, and transforming growth factor β1 were detected in the experimental group at 4 weeks (p = 0.041, p = 0.026, and p = 0.041, respectively). This study confirms that polydeoxyribonucleotide can improve the tensile strength of the rats’ Achilles tendon following injury and repair. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1767–1776, 2018.

     

The remodelling process of allogeneic and autogenous patellar tendon grafts in rats: a radiochemical study

In order to study the remodelling of collagen fibres of transplanted tendons, one-half of the patellar tendon of the knee in 54 rats was replaced with a radioisotope (³H-proline)-labelled patellar tendon procured from a donor rat. Three transplantation models were used in this study: fresh-frozen allograft, fresh-frozen autograft (fresh-frozen isograft), and fresh autograft (fresh isograft). The percentage of old collagen was calculated as an indicator of collagen turnover from the amount of hydroxyproline and the radioactivity level of ³H-bydroxyproline in the transplanted tendons at 4, 12 and 24 weeks postoperatively. Histological evaluation was also performed at 2, 4, 12 and 24 weeks. At 4 weeks, the percentage of old collagen in the grafts from the fresh-frozen allograft group was significantly lower than in the autograft groups (20% vs. 48%). Although the percentage of old collagen in the fresh-frozen autograft group had decreased to the same level as in the fresh-frozen allograft group by 12 weeks (approximately 10%), the value was still high in the fresh autograft group at 12 weeks and remained higher (38%). Histologically, at 2 weeks, the cellularity in the fresh-frozen allograft was higher than in the fresh-frozen autograft. After 4 weeks, however, no significant difference was found between these two groups. In the fresh autograft group, the cellularity was lower than in the fresh-frozen groups at all times. In conclusion, the collagen turnover rate in the fresh-frozen allograft was the most rapid of the three transplantation models based on hydroxyproline turnover.     

富血小板血浆对大鼠跟腱断裂早期愈合的影响

目的富血小板血浆(platelet-rich plasma,PRP)具有促进损伤组织修复作用。通过观察PRP局部注射对大鼠跟腱断裂早期愈合的影响,为临床应用提供实验依据。方法 SPF级SD大鼠46只,雌雄不限,体重190～240 g。取10只大鼠心脏动脉血制备PRP及贫血小板血浆(platelet-poor plasma,PPP);其余36只随机分为3组(n=12),分别为空白对照组、PPP组及PRP组。大鼠制备双侧跟腱断裂模型后,PPP组和PRP组跟腱周围局部对应注射PPP及PRP,每侧100μL,每周1次至处死;空白对照组不作处理。术后观察大鼠一般情况,于1、2、3、4周取双侧跟腱,行大体、组织学及免疫组织化学染色观察,测量新生跟腱Ⅰ型胶原纤维含量;并于4周行生物力学测试。结果大鼠均存活至实验完成。随着时间延长,各组大鼠跟腱水肿逐渐减退,滑动性逐渐改善;术后3周内各组跟腱粘连逐渐加重,4周时减轻,1、4周时各组跟腱粘连程度分级差异均无统计学意义(P>0.05)。术后1周PRP组炎性细胞浸润、毛细血管及胶原纤维增殖较空白对照组、PPP组明显,之后炎性反应及毛细血管生成逐渐减少。各时间点各组均可见Ⅰ型胶原纤维阳性表达,术后1、2、3周PRP组Ⅰ型胶原纤维阳性密度值多于空白对照组和PPP组(P<0.05),4周时3组差异无统计学意义(P>0.05)。生物力学测试:术后4周3组跟腱最大滑动距离比较,差异均无统计学意义(P>0.05);PRP组跟腱弹性模量及最大抗拉力明显高于空白对照组及PPP组(P<0.05)。结论大鼠跟腱断裂早期于断端周围注射PRP能促进跟腱愈合。     

The influence of exercise in the healing of the rabbit Achilles tendon

Effect of exercise on tendon healing was studied in partially tenotomized rabbit achilles tendons by post-operatively applying a plaster splint to the right leg from the knee to the end of the toe, but no external fixation to the left leg. The animals were serially sacrificed, and new tendon tissues generated at the tenotomy site were examined. Collagen type analysis of the new tendon tissue showed a nearly constant ratio of type III to type I collagen of about 10% in the fixed side, but in the non-fixed side it showed an increase to 19% 2 weeks after the operation followed thereafter by a gradual decrease. Ultrastructural examination revealed an earlier increase in the diameter of collagen fibers suggesting their faster maturation in the non-fixed side.     

Radix Dipsaci does not improve tendon healing in a rat model of patellar tendon donor site injury

Objective: To explore whether Radix Dipsaci (RD) exhibits beneficial effects on tendon healing. Methods: An attempt was made to explore the in vitro effects of a hot water extract of RD on gene expression of procollagen Type I (COL1A1), procollagen Type III (COL3A1) and decorin in cultured tendon fibroblasts, and its in vivo effects in a well‐established rat model of patellar tendon donor site injury. Results: It was found that gene expression of COL3A1 and decorin in cultured tendon fibroblasts was significantly increased by RD, but that COL1A1 was not affected. In vivo studies showed that RD increased blood vessels in the wound but did not significantly affect the expression of COL1A1, COL3A1 and decorin at day 14 post‐injury. The ultimate tensile stress of the healing tendon was not significantly improved by either local injection or oral administration of hot water extract of RD (P > 0.05). Conclusion: The present findings imply that RD per se does not significantly improve tendon healing. Further investigation of RD in a herbal formula may be necessary to test its efficacy in tendon injuries.     

Effects of low-voltage microamperage stimulation on tendon healing in rats

STUDY DESIGN: Randomized controlled prospective experimental study. OBJECTIVES: To examine the effects of transcutaneous low-voltage microamperage stimulation (LVMAS) on the mechanical strength of Achilles tendon repair in rats at 4 weeks after injury. BACKGROUND: Understanding the effect of LVMAS on the healing of injured tendons is hampered by the lack of related experimental studies, especially from the aspect of biomechanical outcome measures. METHODS AND MEASURES: Fourteen 3-month-old male Sprague-Dawley rats received surgical transection to the medial portion of their right Achilles tendon. The rats were divided into a LVMAS group (n = 7) and control group (n = 7). From day 6 postsurgery onwards, the LVMAS group received daily treatment of transcutaneous LVMAS (2.5 V, 100 microA/cm2, 10 pulses per second, positive current) for a total of 22 sessions, while the control group received placebo LVMAS by the same investigator during that period. On day 31, the Achilles tendons were harvested for biomechanical testing for load relaxation, stiffness, and ultimate tensile strength along the longitudinal direction. RESULTS: The normalized Achilles tendon ultimate tensile strength of the LVMAS group (mean +/- SD, 110.5% +/- 25.0%) was higher than that of the control group (75.3% +/- 20.8%) (P = .014), but no significant difference was found in normalized stiffness and load relaxation between the 2 groups (P = .239 and .350, respectively). CONCLUSION: The results of this study suggest that the administration of transcutaneous LVMAS could improve healing and consequently the tensile strength of partially transected Achilles tendons of rats at 4 weeks after injury.     

Effect of low-level laser therapy on healing of tenotomized Achilles tendon in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is associated with musculoskeletal damage. Investigations have indicated that healing of the surgically tenotomized Achilles tendon was considerably augmented following low-level laser therapy (LLLT) in non-diabetic, healthy animals. The aim of the present study was to evaluate the effect of LLLT on the Achilles tendon healing in streptozotocin-induced diabetic (STZ-D) rats via a biomechanical evaluating method. Thirty-three rats were divided into non-diabetic (n?=?18) and diabetic (n?=?15) groups. DM was induced in the rats by injections of STZ. The right Achilles tendons of all rats were tenotomized 1 month after STZ injections. The two experimental groups (n?=?6 for each group) of non-diabetic rats were irradiated with a helium–neon (He–Ne) laser at 2.9 and 11.5 J/cm² for ten consecutive days. The two experimental groups of diabetic rats (n?=?5 for each group) were irradiated with a He–Ne laser at 2.9 and 4.3 J/cm² for ten consecutive days. The tendons were submitted to a tensiometric test. Significant improvements in the maximum stress (MS) values (Newton per square millimeter) were found following LLLT at 2.9 J/cm² in both the non-diabetic (p?=?0.031) and diabetic (p?=?0.019) experimental groups when compared with their control groups. LLLT at 2.9 J/cm² to the tenotomized Achilles tendons in the non-diabetic and diabetic rats significantly increased the strength and MS of repairing Achilles tendons in our study.     

Fibroma of tendon sheath involving the patellar tendon

Fibroma of tendon sheath is a benign soft-tissue tumor that usually arises in association with tendons or ligamentous structures. We describe, what is, to the best of our knowledge, the first reported case of fibroma of tendon sheath involving the patellar tendon.     

Indomethacin and celecoxib improve tendon healing in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the formation of bone. However, they have been shown to increase tensile strength in healing tendons. Most NSAIDs inhibit two isoforms of cyclooxygenases called Cox-1 and Cox-2. Thanks to fewer side-effects, the recently introduced selective cyclooxygenase-2 (Cox-2) inhibitors will probably promote more widespread use of this kind of drug. To clarify the effects on tendon healing of a general Cox-inhibitor (indomethacin) as well as a selective Cox-2 inhibitor (celecoxib), we resected 3 mm of the Achilles tendon in rats and measured the strength of the tendon regenerate. Indomethacin given as daily injections in doses of 1.5, 3.0 and 5.0 mg/kg reduced the thickness (cross-sectional area) of the tendon regenerate at 14 days, as compared to controls, but there was no difference in the failure load or stiffness. In another series of measurements, indomethacin in a dose of 3.0 mg/kg reduced the cross-sectional area at 10, 14 and 18 days after transsection. Failure load was not affected, but tensile stress at failure was increased by indomethacin at 14 and 18 days. Indomethacin (3 mg/kg) was then compared to celecoxib (4.5 mg/kg) and controls 14 days after tendon transsection. No difference between the drugs was seen. Again, the transverse area was smaller in the treated tendons than in the controls. Failure load was unchanged and the tensile stress was higher in the treated tendons than in the controls. Because of the reduction in cross-sectional area without an effect on failure load, the use of Cox-inhibitors may be beneficial in clinical situations where thickening of a healing tendon is a problem - e.g., in the hand or shoulder.     

Indomethacin and celecoxib improve tendon healing in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the formation of bone. However, they have been shown to increase tensile strength in healing tendons. Most NSAIDs inhibit two isoforms of cyclooxygenases called Cox-1 and Cox-2. Thanks to fewer side-effects, the recently introduced selective cyclooxygenase-2 (Cox-2) inhibitors will probably promote more widespread use of this kind of drug. To clarify the effects on tendon healing of a general Cox-inhibitor (indomethacin) as well as a selective Cox-2 inhibitor (celecoxib), we resected 3 mm of the Achilles tendon in rats and measured the strength of the tendon regenerate. Indomethacin given as daily injections in doses of 1.5, 3.0 and 5.0 mg/kg reduced the thickness (cross-sectional area) of the tendon regenerate at 14 days, as compared to controls, but there was no difference in the failure load or stiffness. In another series of measurements, indomethacin in a dose of 3.0 mg/kg reduced the cross-sectional area at 10, 14 and 18 days after transsection. Failure load was not affected, but tensile stress at failure was increased by indomethacin at 14 and 18 days. Indomethacin (3 mg/kg) was then compared to celecoxib (4.5 mg/kg) and controls 14 days after tendon transsection. No difference between the drugs was seen. Again, the transverse area was smaller in the treated tendons than in the controls. Failure load was unchanged and the tensile stress was higher in the treated tendons than in the controls. Because of the reduction in cross-sectional area without an effect on failure load, the use of Cox-inhibitors may be beneficial in clinical situations where thickening of a healing tendon is a problem - e.g., in the hand or shoulder.     

Indomethacin and celecoxib improve tendon healing in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the formation of bone. However, they have been shown to increase tensile strength in healing tendons. Most NSAIDs inhibit two isoforms of cyclooxygenases called Cox-1 and Cox-2. Thanks to fewer side-effects, the recently introduced selective cyclooxygenase-2 (Cox-2) inhibitors will probably promote more widespread use of this kind of drug. To clarify the effects on tendon healing of a general Cox-inhibitor (indomethacin) as well as a selective Cox-2 inhibitor (celecoxib), we resected 3 mm of the Achilles tendon in rats and measured the strength of the tendon regenerate. Indomethacin given as daily injections in doses of 1.5, 3.0 and 5.0 mg/kg reduced the thickness (cross-sectional area) of the tendon regenerate at 14 days, as compared to controls, but there was no difference in the failure load or stiffness. In another series of measurements, indomethacin in a dose of 3.0 mg/kg reduced the cross-sectional area at 10, 14 and 18 days after transsection. Failure load was not affected, but tensile stress at failure was increased by indomethacin at 14 and 18 days. Indomethacin (3 mg/kg) was then compared to celecoxib (4.5 mg/kg) and controls 14 days after tendon transsection. No difference between the drugs was seen. Again, the transverse area was smaller in the treated tendons than in the controls. Failure load was unchanged and the tensile stress was higher in the treated tendons than in the controls. Because of the reduction in cross-sectional area without an effect on failure load, the use of Cox-inhibitors may be beneficial in clinical situations where thickening of a healing tendon is a problem--e.g., in the hand or shoulder.     

肩袖损伤后修复的实验研究

目的观察肩峰下撞击征所致肩袖损伤后的修复反应及碱性成纤维细胞生长因子(basicfibroblastgrowthfactor,bFGF)的表达。方法雄性SD大鼠50只,剪取同侧肩胛冈骨块移位于肩峰底面,建立肩峰下撞击模型,对侧行假手术作为对照。分别于术后第3、7、14、28、56d处死动物,切取整个肩关节,观察冈下肌肌腱的修复反应及bFGF的表达,并使用计算机图像分析系统检测bFGF的表达变化,图像分析结果中光密度值(OD)和阳性面积值分别表示bFGF的表达强度和阳性细胞数。结果所有动物实验侧的冈下肌肌腱均出现滑囊面撕裂,肌腱断端细胞增生,来自肩峰下滑囊的结缔组织覆盖其表面。对照侧冈下肌肌腱完好,仅有少量的腱细胞和滑囊细胞表达bFGF;而实验侧沿腱外膜排列的腱细胞、从肩峰下滑囊迁移的炎细胞和成纤维细胞表达信号增强。结论肌腱损伤后bFGF的表达增强;肩峰下滑囊是肩袖修复的基础和bFGF分泌的主要来源,修补肩袖时应尽量给予保留。     

Pyridinoline in relation to ultimate stress of the patellar tendon during healing: An animal study

The ultimate stress of the central one-third of the patellar tendon was studied in a gap wound-healing model in the rat. The specimens were also analyzed for collagen and nonreducible crosslinks, as measured by hydroxyproline and pyridinoline content, respectively. Thirty days after injury, the ultimate stress of the healing patellar tendon was restored to an average of 71% of the control value and remained constant over time. The pyridinoline content of the healing tendon was twice the control value by 30 days after injury and reached a plateau; however, the hydroxyproline content did not change significantly over time. Stepwise regression analysis demonstrated that pyridinoline was a better biochemical marker for ultimate stress than was hydroxyproline. The current study provides insights into the functional behaviour of the healing patellar tendon by establishing the relationship between the two biochemical components and the ultimate stress of the healing patellar tendon. This study also suggests the possibility of using pyridinoline content as an indirect marker of the ultimate stress because in vivo assessment is impossible.