Morphological study of mechanoreceptors in collateral ligaments of the ankle joint
Wu et al. Journal of Orthopaedic Surgery and Research
Morphological study of mechanoreceptors in collateral ligaments of the ankle joint
Xiaochuan Wu 2
Weidong Song 0
Cuihuan Zheng 1
Shixiong Zhou 4
Shengbin Bai 3
0 Department of Orthopaedics, Sun Yat-sen Memorial Hospital , 107 Riverside Road, Guangzhou, Guangdong Province 510120 , China
1 Intensive Care Unit, Sanxiang Hospital , Zhongshan, Guangdong Province 528463 , China
2 Department of Orthopaedics, Sanxiang Hospital , Zhongshan, Guangdong Province 528463 , China
3 Department of Histology and Embryology, Xinjiang Medical University , Urumqi, Xinjiang Province 830054 , China
4 Department of Histology and Embryology, Guangdong Medical College , Zhanjiang, Guangdong Province 523000 , China
Background: The aim of this study was to analyze the pattern and types of sensory nerve endings in ankle collateral ligaments using histological techniques, in order to observe the morphology and distribution of mechanoreceptors in the collateral ligaments of cadaver ankle joint, and to provide the morphological evidence for the role of the ligament in joint sensory function. Methods: Twelve lateral collateral ligaments including anterior talofibular ligament (ATFL; n = 6), posterior talofibular ligament (PTFL; n = 6), and calcaneofibular ligament (CFL; n = 6) were harvested from six fresh frozen cadavers. The ligaments were embedded in paraffin, sectioned at 4 μm, and then stained using a modified gold-chloride staining methods. The collateral ligament was divided into three segments: proximal, middle, and distal segments. Fifty-four ATFL slides, 90 PTFL slides, and 108 CFL slides were analyzed. Mechanoreceptors were classified based on Freemen and Wyke's classification. Mechanoreceptor distribution was analyzed statistically. One-way ANOVA (postHoc LSD) was used for statistical analysis. Results: All the four typical types of nerve endings (the Ruffini corpuscles, Pacinian corpuscles, Golgi tendon organs, and free nerve endings) were identified in these ligaments. Pacinian corpuscles were the predominant in all four complexes. More mechanoreceptors were found in synovial membrane near both ends of the ligaments attached to the bone. No statistical differences were found in the amount of mechanoreceptors among distal, middle, and proximal parts of the ligaments. Conclusions: The four typical types of mechanoreceptors were all identified in the collateral ligaments of the human ankle. Pacinian corpuscles were the predominant in all four complexes. This indicates that the main function of ankle collateral ligaments is to sense joint speeds in motions.
Morphology; Mechanoreceptors; Collateral ligaments; Ankle joint; Pacinian corpuscles
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Introduction
Ankles are the most important large joints of shock
absorption and load bearing. The ankle sprain is one of the
most common sports injuries in clinic [1]. It happens
when stepping on uneven ground or on some object,
with the movement of excessive plantar flexion and
ankle inversion. As the lateral ligaments are weaker than
the medial ligament and the inversion muscle group is
stronger than the eversion muscle group, the lateral
ligaments are likely to be injured, taking up about 85 % of
the ankle sprain [2]. As the collateral ligaments play an
important role in the structural stability of the ankle, the
biomechanical stability will be disturbed after injury.
In addition to biomechanical function, the collateral
ligaments also contribute to the proprioceptive function
[3, 4]. Once injured, it can disturb not only the
proprioceptive information input but also the coordination
control of the nerve center to the complex of the joint
nerve muscle, leading to functional instability of the
ankle [5]. In clinic, the main purpose to treat ankle
sprain and ankle joint instability is to restore the
structural stability of the ankle. There are dozens of operation
methods, while the outcome is not satisfied [6]. It has
been reported that the curative satisfactory outcomes of
lateral ligament injury are correlated to functional
instability, not the mechanical instability [7]. As the
importance of restoring the proprioceptive function has
long been neglected, the chance of chronic ankle
instability increases greatly [8, 9]. To better understand
the function of the ankle collateral ligament, the
microcosmic studies of the mediating organs in the ligament
have been performed [10–14]. The proprioceptive loss
and restore in lateral ankle sprain (LAS) and chronic
ankle instability (CAI) are becoming a hot spot in the
sports medicine and orthopedics research [15, 16]. The
morphology, classification, distribution, and mechanisms
have not completely reached consensus, which hinders
the treatment research of the functional instability. The
purpose of this study was to understand neural anatomic
function of the ankle collateral ligament, so that to
provide rationale for joint surgical treatment.
This study focused on the morphological structu (...truncated)