Histomorphometric analysis of innervation of the anterior cruciate ligament in osteoarthritis

Preservation of the Tibial Remnant in Anterior Cruciate Ligament Reconstruction May Improve Postoperative Proprioceptive Function

The purpose of this study was to retrospectively compare clinical results, including proprioceptive function, after anterior cruciate ligament (ACL) reconstruction between 2 groups using techniques that preserve and eliminate the tibial remnant. Forty-eight patients who were followed for at least 24 months after ACL reconstruction with 4-strand hamstring tendon autografts were enrolled in this study. They were then divided into 2 groups: the remnant-preserving group (group A, 26 patients), in whom more than 7 mm of the remnant tibial stump (approximately 20% of the mean length of the ACL) was preserved; and the remnant-eliminating group (group B, 22 patients), in whom the tibial remnant was eliminated during ACL reconstruction. The average duration of follow-up was 25.5 months. At last follow-up, patients were evaluated using the International Knee Documentation Committee scale, Hospital for Special Surgery score, Lachman test, arthrometer, reproduction of passive positioning (RPP) test, threshold to detection of passive motion (TTDPM) test, one-leg hop test, and single-limb standing test. The clinical results between the 2 groups were statistically compared. Group A showed significantly better results on the RPP test at 15° (P=.040) and 30° (P=.010), one-leg hop test (P=.017), and single-limb standing test (P=.007) compared with group B. The other results showed no significant differences. The remnant-preserving technique in ACL reconstruction yields better proprioceptive and functional outcomes and may help achieve postoperative patient satisfaction. [Orthopedics. 2020;43(4):e231-e236.].

Study of the Nerve Endings and Mechanoreceptors of the Anterolateral Ligament of the Knee

PURPOSE

To describe the morphology and distribution of the anterolateral ligament of the knee (ALL) nerve endings, aiming to understand the interaction between the proprioceptive system and knee mechanics.

METHODS

Twenty ALLs were obtained from fresh frozen cadavers. The ligaments were measured, weighed, and cut. Sections (10 μm) were prepared in hematoxylin and eosin-stained slides to analyze tissue integrity, and 50-μm sections were subjected to immunofluorescence with the protein gene product 9.5 as primary antibody and Alexa Fluor 488 as secondary antibody, followed by microscopic analysis.

RESULTS

The ALL was identified in 100% of the dissections, exhibiting a mean (± standard deviation) length of 4.0 ± 0.4 cm, a mean width of 5.5 ± 0.8 mm, and a mean weight of 0.9 ± 0.2 g. The histological sections in hematoxylin and eosin showed dense, well-organized collagen and the presence of vascular tissue. All the specimens analyzed contained type I (Ruffini-like) mechanoreceptors and free nerve endings (type IV), varying from parallel to intertwined fibers. Unclassified nerve endings with different irregular shapes were also found. The neural elements occupied 0.6% ± 0.3% of the ligament area, and most were observed near the origin of ALL insertions.

CONCLUSION

The ALL exhibits a peripheral nerve structure, primarily type I and IV mechanoreceptors. These findings suggest that the ALL is important for the proprioception and anterolateral stabilization of the knee.

CLINICAL RELEVANCE

It is important to understand ALL innervation and infer how an injury could compromise the proprioceptive role of the lateral compartment, as the ligaments contribute dynamically to stability through proprioceptive control of muscle forces. The findings confirm that the ALL is highly innervated by mechanoreceptors and may have a proprioceptive role in conjunction with the lateral collateral ligament in the lateral region of the knee.

Reduced Anterior Cruciate Ligament Vascularization Is Associated With Chondral Knee Lesions

This study tested the association between periligamentous vascularization of the anterior cruciate ligament (ACL) and the presence of chondral knee lesions via retrospective analysis of prospectively collected data from 702 consecutive knee arthroscopic procedures. In each case, the ACL periligamentous envelope was documented as follows: (1) vascular, where the ACL was covered with blood vessels along its entire length; (2) centrally avascular, where the central third of the ACL was not covered but peripheral vascularized coverage was present; and (3) avascular, where there was no blood vessel coverage of the ACL. Inclusion criteria for the study were as follows: (1) age older than 18 years and (2) normal knee ligament laxity. Univariate analysis and multiple logistic regression were used to test the association between chondral lesions and each of the variables: sex, age, meniscus tear, decreased ACL vascularity, and concomitant chondral lesion in another knee compartment. The cohort included 516 knees. In the univariate analysis, all variables were associated with a chondral lesion, but only older age and decreased ACL vascularity were associated with chondral lesions in each knee compartment. In the regression model, only decreased ACL vascularity was associated with chondral lesions in each knee compartment. For avascular knees, the odds ratio was 2.84 for medial femoral condyle lesions (95% confidence interval, 1.73-4.68; P=.000), 2.44 for lateral femoral condyle lesions (95% confidence interval, 1.19-5.03; P=.015), and 2.48 for patellofemoral lesions (95% confidence interval, 1.55-3.97; P=.000). The findings showed that decreased ACL periligamentous vascularization is associated with chondral lesions of the femoral condyles in knees with preserved ACL laxity. [Orthopedics. 2016; 39(4):e737-e743.].

Posterior cruciate mechanoreceptors in osteoarthritic and cruciate-retaining TKA retrievals: a pilot study

BACKGROUND

Although normal cruciate ligaments and those in patients with osteoarthritic (OA) knees contain mechanoreceptors, it is unclear whether they are present after functioning in a cruciate-retaining total knee arthroplasty (TKA).

QUESTIONS/PURPOSES

We therefore determined if the areas occupied by mechanoreceptors in the human posterior cruciate ligament (PCL) are similar in patients with osteoarthritis and in patients who have had TKA with retention of the PCL.

METHODS

We identified five cruciate-retaining TKA specimens from a retrieval program and obtained five PCLs during cruciate-sacrificing TKA from patients with OA; the retrieved specimens had been in place 5 to 12 years. The whole en bloc PCL specimens were harvested for the study. These specimens were then sectioned to a thickness of 8 μm and mounted on microscope slides. Two transverse cross-sections from the distal third from each specimen 100 μm apart were then subjected to immunohistochemistry with neurofilament protein (NFP) and S-100 protein.

RESULTS

All five PCL specimens in each group revealed multiple areas of positive stained elements with both S-100 protein and NFP immunohistochemical staining. Morphologically, these elements appear to correspond to Pacinilike, Golgilike, and fusiform types of mechanoreceptors. We observed no difference in positive staining mechanoreceptor elements as a percentage of area in the osteoarthritis and TKA groups.

CONCLUSION

Mechanoreceptors appear to occupy similar areas before and after implantation of a TKA.

CLINICAL RELEVANCE

If mechanoreceptors continue to function after cruciate-retaining TKA, then it may continue to participate in proprioception of the knee after TKA.

The characteristics of the mechanoreceptors of the hip with arthrosis

Mechanoreceptors have been extensively studied in different joints and distinct signals that convey proprioceptive information to the cortex. Several clinical reports have established a link between the number of mechanoreceptors and a deficient proprioceptive system; however, little or no literature suggest concentration of mechanoreceptors might be affected by hip arthrosis. The purpose of this study is first to determine the existence of mechanoreceptors and free nerve endings in the hip joint and to distinguish between their conditions: those with arthrosis and without arthrosis. Samples of 45 male hips were analyzed: 30 taken from patients with arthrosis that were submitted to total arthroplasty and 15 taken from male cadavers without arthrosis. The patients' ages ranged from 38 to75 years (average 56.5) and the cadavers' ages ranged from 21 to 50 years (average 35.5). The capsule, labrum, and femoral head ligament tissues were obtained during the arthroplasty procedure from 30 patients with arthrosis and from 15 male cadavers. The tissue was cut into fragments of around 3 mm. Each fragment was then immediately stained with gold chloride 1% solution and divided into sections of 6 μm thickness. The Mann-Whitney test was used for two groups and the ANOVA, Friedman and Kruskal-Wallis tests for more than two groups. Results show the mechanoreceptors (Pacini, Ruffini and Golgi corpuscles) and free nerve endings are present in the capsule, femoral head ligament, and labrum of the hip joint. When all the densities of the nerve endings were examined with regard to those with arthrosis and those without arthrosis, the mechanoreceptors of cadavers without arthrosis were found to be more pronounced and an increase in free nerve endings could be observed (p = 0.0082). Further studies, especially electrophysiological studies, need to be carried out to clarify the functions of the mechanoreceptors in the joints.

Mechanoreceptors found in a posterior cruciate ligament from a well-functioning total knee arthroplasty retrieval

Histologic analysis of the posterior cruciate ligament has been reported in the normal and osteoarthritic knee but not after cruciate-retaining (CR) total knee arthroplasty (TKA). Retention of the posterior cruciate ligament during TKA has been debated as to whether it is beneficial in stability and function. If the presence of mechanoreceptors is shown to be maintained in CR TKA, then there may be an argument for retention. This case report used a retrieval of a well-functioning TKA specimen that had a CR TKA. To prove the presence of mechanoreceptors within the ligament, immunohistochemistry techniques using S100 protein and neurofilament protein were used. This specimen had pacini and lamellar type of mechanoreceptors present on immunohistochemistry analysis. The presence or retention of mechanoreceptors and innervations of the ligament may indicate an advantage when retained during TKA.

Cruciate ligaments in arthritic knees: a histologic study with radiologic correlation

Anterior cruciate ligaments (ACLs) and posterior cruciate ligaments (PCLs) from 45 osteoarthritic knees were histologically examined to evaluate the frequency and grade the severity of degenerative changes, which were correlated with radiologic grade of arthritis and severity of deformity at the knee. Immunohistochemical staining was used to identify neurofilaments in 10 knees. A histologic score was generated for both cruciates based on changes found on light microscopy. The ACL was severely degenerated, absent, or disrupted in knees with radiologic arthritis higher than grade 3 and varus deformity exceeding 15 degrees . The PCL was moderately degenerated in most knees irrespective of the grade of arthritis and severity of deformity. Neurofilaments were present in all 10 PCLs and absent in 4 ACLs.

Histomorphometric evaluation of mechanoreceptors and free nerve endings in human lateral ankle ligaments

INTRODUCTION

Joint mechanoreceptors have been studied and most of investigators recognize the potential role of mechanoreceptors in the proprioceptive function of joint. The aim of this study was to analyze the general innervation and the possible existence of sensory receptors in the lateral ankle ligament.

METHODS

Lateral ankle ligaments including anterior talofibular, posterior talofibular and calcaneofibular were obtained from 24 ankles of 13 male cadavers with ages ranging from 18 to 65 (mean 41.6) years. Each ligament was divided into three parts according to the bony attachments (proximal, central, and distal segments). Histologically mechanoreceptors (Ruffini, Pacini and Golgi) and free nerve endings were identified, and classified. Histomorphometric determination and evaluation of the density of the area of the receptor was performed by the point-counting methods.

RESULTS

The anterior talofibular, posterior talofibular, and calcaneofibular ligaments were endowed with mechanoreceptor and free nerve endings. There was a significant prevalence of Pacini (p<0.001) compared with Ruffini and Golgi. However, there was no significant difference in the mechanoreceptors density in the different ligaments analyzed (p>0.05)

CONCLUSION

Innervation of the lateral ankle ligaments was confirmed in this study, suggesting that the presence of mechanoreceptors could have clinical implication as well as relevance in the proprioceptive function. Future electrophysiological studies will be required to define the role in the proprioceptive and nociceptive system of the ankle.

Distribution of nerve endings in the human dorsal radiocarpal ligament

PURPOSE

The purpose of this investigation was to evaluate the nerve-ending apparatus populations within a large number of adult human dorsal radiocarpal (DRC) ligaments to test the hypothesis that the majority of nerve endings could be grouped into established classifications and that the nerve endings could be found in predictable locations within the substance of the ligament.

METHODS

The DRC ligaments were harvested from 20 wrists of 10 fresh cadavers with an average age of 75.6 years within 12 to 18 hours of death. Before the tissues were harvested, radiographs were taken to exclude any arthritic conditions of the wrists. Tissues were fixed, sectioned with a cryostat, and serial sections were collected on glass slides. Slides were processed for fluorescence immunohistochemistry using antibody to protein gene product 9.5 and a secondary antibody conjugated to a fluorescent tag (Alexa Fluor 488). The sections were evaluated with an LSM-510 confocal laser microscope and a Kontron KS 400 image analyzer. Labeled nerve endings were counted, mapped, and reconstructed.

RESULTS

The average number of nerve endings in each DRC ligament was 10.1+/-4.7. More than 76% of the nerve endings were found in the 2 ends of the ligament with 23.3% in the central third and approximately 80% distributed in the superficial layer. More than 80% of the nerve endings were discovered in the epiligamentous sheath rather than in the perifascicular spaces.

CONCLUSIONS

The distribution of the nerve endings follows a consistent pattern. These results will provide a foundation of morphologic information useful in understanding normal and abnormal neural control of wrist joint mechanics.

Combining the gold chloride and toluidine blue stains to investigate chick embryo neural tissue

Toluidine blue and gold chloride stains are both well-known for staining nervous tissue. Toluidine blue is a general method to stain neurons and glia, used because of the speed of action. Gold sublimate is a delicate procedure that requires extreme purity of reagents and materials, and it stains astrocytes and neurons. The aim of this study was to combine these two special staining methods for embryonic neural tissue and to obtain a repeatable and easily manageable new staining method with improved overall visualization of neural tissue. Fertilized Broiler hatching eggs were incubated at 36 degrees C and on day 8 prepared for histology. Sections were cut at 7 microm thickness and slides were stained for 30 s using a 0.1% Toluidine blue solution. These slides were rinsed with dH2O followed by placing them in gold sublimate for 4 h at room temperature in the dark. Rinsing with dH2O and transferal to a 5% sodium thiosulfate solution was done, followed by another rinsing and mounting of slides. Results showed that the combination of the two methods offers a fast, reliable method with which chick embryonic neural tissue can be evaluated.

Physical characteristics of the axial interosseous ligament of the human sacroiliac joint

BACKGROUND CONTEXT

Although the sacroiliac joint has occupied a place in medical literature since at least the eighteenth century, its role in normal function and dysfunction of the back and hip remains controversial. The controversy persists, because there is still no suitable method to study the role of stability and mobility at the sacroiliac joints in vivo. One cost-effective approach to understanding such complex, deeply placed structures is biomechanical modeling. Unfortunately, very few data on the mechanical properties of tissues in this region are currently available to modelers.

PURPOSE

The objective of this preliminary project was to determine some mechanical properties of the axial interosseous ligament (AIL), and to investigate the histology of the ligament.

STUDY DESIGN/SETTING

A modified split plot design was used in conjunction with descriptive statistics to identify AIL characteristics.

PATIENT SAMPLE

This was a cadaveric study.

OUTCOME MEASURES

The study used descriptive statistics to categorize the ultimate failure strength of the AIL, and to describe the macro-constituents of the ligament.

METHODS

Eighteen sacroiliac joints were harvested from nine fresh female cadavers (age range, 54 to 92). Data from 10 joints submitted to mechanical testing are reported. The eight remaining joints were used for histologic analysis of the AIL by light microscopy.

RESULTS

The AIL proved to be relatively weak, with a mean failure load of 381 N (SD 43.7N) and a peak stress of 1.73 MPa (SD 0.99 MPa). Histologically, the AIL contained significantly less collagen than most other "typical" ligaments.

CONCLUSIONS

The AIL failure loads are just slightly higher than those for the ligamentum flavum in the spine, a tissue composed mainly of elastic fibers. In contrast, the AIL has negligible elastin content. Because the AIL represents about 14% of the total area of interosseous sacroiliac ligaments, its mechanical properties should be useful to modelers of the joint. In addition, it appears that injury to the AIL would do little to compromise the mechanical integrity of the sacroiliac joint. Further study of this ligament seems warranted.