Dacron augmentation in anterior cruciate ligament reconstruction in dogs

Substitution of the central third of the patellar tendon for the deficient anterior cruciate ligament was performed in 12 dogs (24 knees). In one-half of the knees the patellar tendon grafts were "augmented" with a 4-mm woven Dacron graft. It was hypothesized that Dacron augmentation would protect the patellar tendon graft during its revascularization stages. This was not the case, however. Only once did a Dacron ligament graft demonstrate superiority over the nonaugmented graft; indeed, five of the augmented grafts performed significantly worse.     

The morphological effects of synthetic augmentation in posterior cruciate ligament reconstruction

The treatment of posterior cruciate ligament (PCL) injuries remains controversial. Due to various problems, PCL reconstruction has not consistently produced the knee stability desired. Biological graft tissue undergoes a remarkable healing process comprising different phases. The strength of autogenous graft material decreases soon after operation. During this early healing phase synthetic augmentation could protect the graft tissue from overloading or overstretching, supporting the tissue revitalization and remodeling process. In order to evaluate the morphological effects of the ligament augmentation device (LAD) on a free patellar tendon autograft in PCL reconstruction, a comparative study in sheep was conducted. In 24 mature sheep, the PCL was replaced with either a patellar tendon autograft alone or a patellar tendon autograft augmented by the LAD. The LAD was fixed at both ends. After the operation the animals were not immobilized. Tibial fixation was released 8 weeks postoperation. The autografts of both groups were histologically evaluated after 2, 6, 16, 26, 52, and 104 weeks. In addition to necrotic and degenerative alterations, a remarkable inflammatory reaction could be seen in the LAD-augmented autografts early postoperation. Compared with the nonaugmented autografts, tissue formation and remodeling were delayed in the augmented group. After 1 and 2 years, the morphology of the autograft tissue was similar in both the augmented and nonaugmented group and differed from that of a normal PCL. The LAD was surrounded by a chronic inflammatory reaction, and collagen fiber ingrowth into the LAD was not observed. Using transmission electron microscopy, small diameter collagen fibrils were predominant in the graft tissue of both groups. Thus, a better remodeling of the autograft tissue in the presence of the LAD could not be demonstrated in this particular study. The value of synthetic augmentation of biological grafts in PCL reconstruction seems to be questionable at present.Supported by the Deutsche Forschungsgemeinschaft     

Use of a bioscaffold to improve healing of a patellar tendon defect after graft harvest for ACL reconstruction: A study in rabbits

Following harvest of a bone‐patellar tendon‐bone (BPTB) autograft, the central third of the patellar tendon (PT) does not heal well. The healing tissues also form adhesions to the fat pad and can cause abnormal patellofemoral joint motion. The hypotheses were that a bioscaffold could enhance patellar tendon healing through contact guidance and chemotaxis, and the scaffold could serve as a barrier to decrease adhesion formation between the neo‐PT and infrapatellar fat pad. In 20 New Zealand White rabbits, a central‐third PT defect was created. One strip of porcine small intestinal submucosa (SIS) was attached to both the anterior and posterior sides of the PT defect of the SIS‐treated group (n = 10). For comparison, a central defect was left nontreated (n = 10). At 12 weeks, histomorphology was examined using Masson's trichrome staining. The cross‐sectional area (CSA) was determined with a laser micrometer, and the central BPTB complexes were tested in uniaxial tension. SIS‐treated samples showed a greater amount of healing tissue with denser and well‐oriented collagen fibers and more spindle‐shaped cells. There was no noticeable adhesion formation in the SIS‐treated group. For the nontreated group, there were significantly more and diffuse adhesive formations. The SIS‐treated group also had a 68% increase in neo‐PT CSA, 98% higher stiffness, and 113% higher ultimate load than that in the nontreated group. SIS treatment increased the quantity of healing tissue, improved the histological appearance and biomechanical properties of the neo‐PT, and prevented adhesion formation between the PT and fat pad. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:255–263, 2008     

Lengthening of anterior cruciate ligament graft

32 patients with old anterior cruciate ligament injuries were operated on with patellar tendon-prepatellar tissue-quadriceps tendon graft over the top without and with augmentation (Kennedy-LAD). The anteroposterior (AP) laxity was assessed preoperatively, and at 6, 12, and 24 months after the operation with roentgen stereophotogrammetry. 6 months postoperatively the instability had decreased 5.4 mm in the nonaugmented and 1.9 mm in the augmented group, but not to normal values. During the following 18 months the AP laxity increased and returned to the preoperative level. At 2 years, 28 of the 32 patients were considered good or excellent, according to the Lysholm score. There was a lack of correlation between AP laxity and functional tests.     

Lengthening of anterior cruciate ligament graft. Roentgen stereophotogrammetry of 32 cases 2 years after repair.

32 patients with old anterior cruciate ligament injuries were operated on with patellar tendon-prepatellar tissue-quadriceps tendon graft over the top without and with augmentation (Kennedy-LAD). The anteroposterior (AP) laxity was assessed preoperatively, and at 6, 12, and 24 months after the operation with roentgen stereophotogrammetry. 6 months postoperatively the instability had decreased 5.4 mm in the nonaugmented and 1.9 mm in the augmented group, but not to normal values. During the following 18 months the AP laxity increased and returned to the preoperative level. At 2 years, 28 of the 32 patients were considered good or excellent, according to the Lysholm score. There was a lack of correlation between AP laxity and functional tests.     

Assessing the strength of the anterior cruciate ligaments and transplants from the central third of the patellar ligament

Tensile strength and elongation tests were applied to bone-ligament-bone specimens of anterior cruciate ligaments and grafts from the central third of patellar tendons of 16 autopsy knee joints. A comparison of all strength values thus recorded has revealed that a graft from the central third of the patellar tendon is a fully effective substitute for anterior cruciate ligaments. No significant difference was found to exist between both variants with regard to percentual elongation and stiffness. Tensile strength of patellar tendon grafts was higher by almost one third as compared to tensile strength recorded from anterior cruciate ligaments.     

Cytokine-induced tendinitis: a preliminary study in rabbits.

This study was designed to determine the effects of a single injection of a species-specific preparation of cytokines into rabbit patellar tendons and to compare the results with a known model of tendinitis, the collagenase-injection model. New Zealand White rabbits were divided into two groups and two time periods (4 and 16 weeks) and injected in the midsubstance of the right patellar tendon with either cytokines or collagenase under ultrasound guidance to confirm intratendinous needle placement. The left patellar tendon was injected with 0.025 ml of saline solution and served as a control. The rabbits were returned to cage activity after injection. At death, two rabbits in each group underwent histological analysis; the remaining eight animals in each time frame were evaluated biomechanically and then biochemically with use of the patella/whole patellar tendon/tibia complex. Histologic results at 4 weeks in the tendons injected with cytokines demonstrated increased cellularity, which was resolving by 16 weeks. The matrix appeared unchanged. The tendons injected with collagenase demonstrated increased angiogenesis of the matrix, hypercellularity, and fibrosis around the tendon at 4 weeks. At 16 weeks, myxoid changes, focal fibrosis, and collagen-bundle disarray with persistent increase in cellularity were noted. Biomechanically, a significant decrease in ultimate load at 16 weeks was seen in the tendons injected with cytokines but no change was seen in cross-sectional area. The tendons injected with collagenase demonstrated a significant increase in cross-sectional area at 4 and 16 weeks compared with those injected with cytokines. Biochemically, there was no significant difference in collagen content between the two groups at 4 or 16 weeks but the tendons injected with collagenase demonstrated a significant increase in crosslinking at 16 weeks. Our conclusion is that the tendons injected with the cytokine preparation represent a model of mild, seemingly reversible tendon injury. The cytokine preparation produces no matrix damage or evidence of collagen degradation and is species specific.     

Combined intra-articular and extra-articular reconstructions for anterior tibial subluxation

This article describes several procedures that combine intra-articular techniques with extra-articular techniques to stabilize the knee with anterior tibial subluxation. The procedures detailed are reconstruction using the semitendinosus tendon and the iliotibial tract; tenodesis using a strip of iliotibial tract combined with intra-articular reconstruction of the anterior cruciate ligament with the central third of the patellar tendon; "mini-reconstruction"; and a procedure utilizing a vascularized patellar tendon graft plus "dynamic" augmentation.     

Augmentation of anterior cruciate ligament reconstruction in dogs with prostheses of different stiffnesses

The purpose of this study was to investigate the biological and biomechanical properties of anterior cruciate ligament (ACL) reconstruction augmented with Dacron prostheses of three different stiffnesses. The ACLs of 36 adult mongrel dogs were removed and the ligament was reconstructed. In 18 dogs, one knee was reconstructed with patellar tendon alone, and the contralateral knee with Dacron augmented patellar tendon. In the remaining 18 dogs, reconstruction was with Dacron augmented patellar tendon with Dacron alone being used for the contralateral control knee. Death was 3 months after surgery, and the reconstructions were examined biologically and biomechanically. The mechanical data were compared with immediate postoperative data obtained from 45 reconstructed fresh cadaveric knees. Tensile testing demonstrated that an increase in failure load was found when the implanted patellar tendon graft was compared with the cadaveric reconstruction. The strength of the Dacron augmented reconstruction showed little change while the Dacron alone graft decreased in strength during the period of implantation. No clear difference was found between the performance of augmentation devices of different stiffnesses. Microangiography showed that grafts were totally revascularized in patellar tendon alone, but not well revascularized in Dacron augmented patellar tendon and Dacron alone reconstruction. The presence of the Dacron appeared to have an adverse effect on revascularization.     

Donor-site morbidity and anterior knee problems after anterior cruciate ligament reconstruction using autografts

The authors review the current knowledge on donor site–related problems after using different types of autografts for anterior cruciate ligament (ACL) reconstruction and make recommendations on minimizing late donor-site problems. Postoperative donor-site morbidity and anterior knee pain following ACL surgery may result in substantial impairment for patients. The selection of graft, surgical technique, and rehabilitation program can affect the severity of pain that patients experience. The loss or disturbance of anterior sensitivity caused by intraoperative injury to the infrapatellar nerve(s) in conjunction with patellar tendon harvest is correlated with donor-site discomfort and an inability to kneel and knee-walk. The patellar tendon at the donor site has significant clinical, radiographic, and histologic abnormalities 2 years after harvest of its central third. Donor-site discomfort correlates poorly with radiographic and histologic findings after the use of patellar tendon autografts. The use of hamstring tendon autografts appears to cause less postoperative donor-site morbidity and anterior knee problems than the use of patellar tendon autografts. There also appears to be a regrowth of the hamstring tendons within 2 years of the harvesting procedure. There is little known about the effect on the donor site of harvesting fascia lata and quadriceps tendon autografts. Efforts should be made to spare the infrapatellar nerve(s) during ACL reconstruction using patellar tendon autografts. Reharvesting the patellar tendon cannot be recommended due to significant clinical, radiographic, and histologic abnormalities 2 years after harvesting its central third. It is important to regain full range of motion and strength after the use of any type of autograft to avoid future anterior knee problems. If randomized controlled trials show that the long-term laxity measurements following ACL reconstruction using hamstring tendon autografts are equal to those of patellar tendon autografts, we recommend the use of hamstring tendon autografts because there are fewer donor-site problems.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 9 (November-December), 2001: pp 971–980     

Hoffa's fat pad resection in total knee arthroplasty

The authors have studied the consequences of resection of Hoffa's fat pad during total knee arthroplasty (TKA). Sixty eight patients undergoing primary TKA were randomised to have Hoffa's fat pad either resected or preserved. Biopsy specimens of Hoffa's fat pad were taken for pathological study in all patients. Radiological, functional and clinical evaluation was made after surgery, before discharge from hospital, after one month and after six months. Thirty six percent of the patients were found to present inflammatory infiltration of Hoffa's fat pad, and severe fibrosis was found in 33 %. A progressive decrease in postoperative anterior knee pain was found in 95% of the patients in both groups. Hoffa's fat pad resection did not appear to result in a change in patellar tendon length during the first six months after TKA. Preoperative fibrosis of Hoffa's fat pad may play a role in postoperative pain and range of motion.     

Effects of harvesting the central third of the patella tendon on the kinetics of the knee joint and the retropatellar pressure

AIM: This biomechanical study was performed to evaluate the consequences of removing the central part of the patellar tendon on the kinematics and kinetics of the femoro-patellar joint. The tendonectomy was performed in the same manner as is frequently done during anterior cruciate ligament reconstructions. Of particular interest in this study was to identify potential factors of the patellar tendon resection which could result in anterior knee pain. METHOD: A simulated isokinetic knee extension from 120 degrees of flexion to full extension was performed on nine human knee cadaver specimens. Joint kinematics was evaluated with ultrasound sensors, and retropatellar contact pressure was measured using a thin-film resistive ink pressure measuring system. Data were taken before and after resection of the central third of the patellar tendon. RESULTS: Harvesting of the central third of the patellar tendon resulted in an elongation of the remaining patellar tendon by less then 0.5 mm. Furthermore, increases in patellar flexion lower than 1 degree were observed. Small changes in retropatellar pressure were also observed. CONCLUSION: The shortening of the patellar tendon due to tendon removal, as already suggested in several previous studies, is not attributed to the removal of the central portion of the tendon itself, but more likely due to secondary scarring contraction of the tissue. The changes of the patellarkinematics and the retropatellar pressure observed in this study are probably not of any clinical significance.     

Effects of patellar position and defect healing on in vitro stifle joint kinematics following removal of the central one‐third of the patellar tendon in an ovine model

Harvest of the central one‐third of the patella tendon (PT) is routinely performed for anterior cruciate ligament reconstruction (ACLR). Patella infera may ensue. In this study we unilaterally resected the central one‐third of the PT in 20 sheep, without reconstructing or defunctionalizing the native ACL, and examined the effects at 3, 6, 12, and 24 weeks postoperatively on PT length, histological appearance of the donor defect and in vitro stifle joint kinematics. Mean length increases (p > 0.263) in the operated tendons of 0.3%, 2.8%, 0.5%, and 2.4% were observed at 3, 6, 12, and 24 weeks. A significant proximal shift of the patella correlated well with a mean 2.35° retardation of patellar flexion (r = 0.440, p = 0.001). A mean net 4.9° decrease in medial patellar tilt was also observed (p < 0.001), but was not coupled with changes in tibial rotation. Donor defect tissue showed a distinct progression of healing with time, remodeling from dense scar tissue at 3 weeks to bundles of well‐organized collagen enveloped by vascularized loose connective tissue at 24 weeks but was not associated with the restoration of kinematics. These results suggest that resection of the central one‐third of the PT and leaving the defect open in the ovine stifle joint may be associated with increased PT length and changes in patellar kinematics which do not recover 6 months postoperatively. The lack of patella infera may render this animal model unsuitable for the interpretation of joint kinematics following PT resection for human ACLR. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:572–581, 2011     

Knee mechanics after repair of the anterior cruciate ligament A cadaver study of ligament augmentation

An experimental knee-testing system was used to investigate the immediate postoperative mechanical state in knees with nonaugmented and augmented repairs of the anterior cruciate ligament. Ligament, repair tissue, and augmentation forces were measured using buckle transducers, and joint motion was measured using an instrumented spatial linkage during the application of 90 N anteriorly-directed tibial loads to seven fresh knee specimens at 0-90 degrees of flexion. Force and motion data were collected from each knee with an intact and excised anterior cruciate ligament, and after performing (1) a nonaugmented repair and an augmented repair using the Ligament Augmentation Device (3M Company) placed either (2) anatomically through the lateral femoral condyle or (3) in the over-the-top position.

The forces in the nonaugmented repair and the repair with the augmentation in the two positions were greater than the forces in the intact anterior cruciate ligament with the knee under the same anterior loads; this difference from normal was not significant with the over-the-top augmentation. With the augmentation anatomically placed, the load sharing did not reduce the force in the repair tissue as compared with the nonaugmented case. The over-the-top augmentation, on the other hand, lowered the repair tissue forces at extension while avoiding high repair tissue forces in flexion. The tibia was consistently in an externally rotated configuration compared with normal in both the unloaded and anterior load states with all three repair procedures.     

Abnormal tenocyte morphology is more prevalent than collagen disruption in asymptomatic athletes' patellar tendons.

This study investigated the prevalence of each of the four features of patellar tendinosis in asymptomatic athletic subjects undergoing patellar tendon anterior cruciate ligament (ACL) reconstruction. Fifty subjects (39 males and 11 females) undergoing ACL reconstruction using a patellar tendon graft were screened for previous tendon symptoms, training and playing history and had their patellar tendons examined with ultrasound prior to surgery. During surgery, a small piece of proximal posterocentral tendon was harvested, fixed and examined under light microscopy. Histopathological changes were graded for severity. Results demonstrate that 18 tendons were abnormal on light microscopy and 32 were normal. There were no differences between subjects with and without pathology in respect of training, recovery after surgery and basic anthropometric measures. Three tendons were abnormal on ultrasound but only one had proximal and central changes. Tendons showed a consistent series of changes. Tenocyte changes were found in all but one of the abnormal tendons. In all but one of the tendons with increased ground substance there were tenocyte changes, and collagen separation was always associated with both tenocyte changes and increased ground substance. No tendons demonstrated neovascularization. It appears that cellular changes must be present if there is an increase in ground substance, or collagen and vascular changes. Further research is required to confirm these findings.     

Knee mechanics after repair of the anterior cruciate ligament. A cadaver study of ligament augmentation

An experimental knee-testing system was used to investigate the immediate postoperative mechanical state in knees with nonaugmented and augmented repairs of the anterior cruciate ligament. Ligament, repair tissue, and augmentation forces were measured using buckle transducers, and joint motion was measured using an instrumented spatial linkage during the application of 90 N anteriorly-directed tibial loads to seven fresh knee specimens at 0-90 degrees of flexion. Force and motion data were collected from each knee with an intact and excised anterior cruciate ligament, and after performing (1) a nonaugmented repair and an augmented repair using the Ligament Augmentation Device (3M Company) placed either (2) anatomically through the lateral femoral condyle or (3) in the over-the-top position. The forces in the nonaugmented repair and the repair with the augmentation in the two positions were greater than the forces in the intact anterior cruciate ligament with the knee under the same anterior loads; this difference from normal was not significant with the over-the-top augmentation. With the augmentation anatomically placed, the load sharing did not reduce the force in the repair tissue as compared with the nonaugmented case. The over-the-top augmentation, on the other hand, lowered the repair tissue forces at extension while avoiding high repair tissue forces in flexion. The tibia was consistently in an externally rotated configuration compared with normal in both the unloaded and anterior load states with all three repair procedures.     

Influence of the infrapatellar fat pad resection in a synovectomy during total knee arthroplasty in patients with rheumatoid arthritis

Influence of the infrapatellar fat pad resection in a synovectomy during total knee arthroplasty (TKA) was evaluated in patients with rheumatoid arthritis (RA). Our findings for 120 RA patients at 28 to 38 months after surgery showed that (i) a significant decrease in the number of patients with anterior aching discomfort despite a lower-lying patella was seen in patients with infrapatellar synovectomy compared with patients without infrapatellar synovectomy, and (ii) an increase in the number of patients with anterior aching discomfort, significant limited motion, slight quadriceps weakness, and significant shortening of patellar tendon length and patella height were noted among patients with infrapatellar synovectomy, including fat pad resection, than in patients without infrapatellar synovectomy.     

Purified collagen I oriented membrane for tendon repair: An ex vivo morphological study

Injured tendons have limited repair ability after full‐thickness lesions. Tendon regeneration properties and adverse reactions were assessed ex vivo in an experimental animal model using a new collagen I membrane. The multilamellar membrane obtained from purified equine Achilles tendon is characterized by oriented collagen I fibers and has been shown to sustain cell growth and orientation in vitro. The central third of the patellar tendon (PT) of 10 New Zealand White rabbits was sectioned and grafted with the collagen membrane; the contralateral PT was cut longitudinally (sham‐operated controls). Animals were euthanized 1 or 6 months after surgery, and tendons were subjected to histological and Synchrotron Radiation‐based Computed Microtomography (SRµCT) examination and 3D structure analysis. Histological and SRµCT findings showed satisfactory graft integration with native tendon. Histological examination also showed ongoing angiogenesis. Adverse side‐effects (inflammation, rejection, calcification) were not observed. The multilamellar collagen I membrane can be considered as an effective tool for tendon defect repair and tendon augmentation. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 738–745, 2013     

Research on strength of the grafts that are used in anterior cruciate ligament reconstruction]

Reconstruction of the anterior cruciate ligament (ACL) using autogenous tissue is a frequently performed procedure used to restore functional stability in ACL--deficient knees. The purpose of this study was to determine the structural mechanical properties of the ACL and the grafts that are used in anterior cruciate ligament reconstruction. We tested specimens of human tissue including: ACL, medial third patellar tendon B-PT-B, central third patellar tendon B-PT-B, gracilis tendon, semitendinosus tendon (single-stranded, double-stranded and quadrupled-stranded), distal iliotibial tract and plantaris tendon (single-stranded and double-stranded). Specimens were obtained at autopsy from 32 young male cadavers. Biomechanical tests were performed using the FPZ-100 machine (produced by VEB Rauenstein). The following grafts have shown higher values than ACL: quadrupled semitendinosus--229% of ACL, doubled semitendinosus--130% of ACL, central third patellar tendon B-PT-B--114% of ACL and medial third patellar tendon B-PT-B--107% of ACL. The following grafts have shown lower values than ACL: semitendinosus tendon--72% of ACL, gracilis tendon--49% of ACL, distal iliotibial tract--47% of ACL, doubled plantaris--18% of ACL and single plantaris--10% of ACL.     

髌下脂肪垫解剖学观测及其临床意义

目的：为膝关节疼痛的诊和治疗提供解剖学依据。方法：在１２具 对髌下脂肪垫和髌韧带等组织结构进行了观测。结果：髌下脂肪垫表面与髌韧带的后面结合疏松,但与髌骨下缘紧密连结。滑膜覆盖于髌脂肪垫的关节腔内部分,并形成翼状臂。脂肪垫伸向股骨和股骨间在前交韧带之前,形成一繁带附着髁间窝前部,其将脂肪垫系于股骨。胫骨近端的前方与髌韧带之间,形成一系带附着髁间窝前部,其将脂肪垫系于股骨。胫骨近端的前方与髌韧带下部