Nerve supply of anterior cruciate ligaments and of cryopreserved anterior cruciate ligament allografts: a new method for the differentiation of the nervous tissues

Abstract

We investigated the nerve supply of anterior cruciate ligaments ((ACLs) and of cryopreserved bone-ACL-bone allografts in a rabbit model with immunohistochemical methods to establish the distribution pattern of the nervous tissues and to determine the reinnervation rate of ACL allografts. The ACL is innervated by three different classes of nerve fibre: (1) fibres of large diameter, characterized by neurofilament immunoreactivity, which are fast-conducting mechanoreceptive sensory afferents; (2) fibres of small diameter, characterized by substance P-immunoreactivity, which are slow-conducting nociceptive sensory afferents; and (3) sympathetic efferent vasomotor fibres, characterized by their immunoreactivity to the rate-limiting enzyme of noradrenaline synthesis, tyrosine hydroxylase. The ACLs showed numerous fibres of all three nerve classes; as specialised sensory nerve endings only Ruffini corpuscles were observed. All nerve fibres were located subsynovially, none within the collagen core of the ligament itself. No nerve fibres were detected in the ACL allografts at 3 and 6 weeks. Sparse fibres were detected at 12 weeks, while the 24-, 36- and 52-week specimens showed plenty of all three fibre types. No mechanoreceptors were found in the ACL allografts. To our knowledge, this method for the first time allows a differentiation of the nerve fibres of ACLs and ACL allografts into three different nerve fibre classes with known neurophysiological functions.

Immunohistological evaluation of proprioceptive potential of the residual stump of injured anterior cruciate ligaments (ACL)

“…The efficacy of this procedure to pick up proprioceptive fibres in intact ACLs has been established in previous studies [18][19][20][21]. Our study was not just confined to finding mechanoreceptors or proprioceptive fibres on the ACL, but also an attempt to correlate their presence with various clinical and operative findings.…”

“…A few previous studies had used monoclonal antibody to NFP as a standard method to demonstrate proprioceptive fibres in normal ACLs [18,20]; we went a step further and used it for the first time in injured ACLs. Its positivity was easy to pick up by direct evaluation under the light microscope.…”

Sensory nerve endings in the anterior cruciate ligament (Lig. cruciatum anterius) of sheep

“…In our opinion, this can be confirmed beyond doubt only by electron microscopy. Immunohistochemistry as carried out by Fromm et al (1994) cannot clearly identify reinnervation of lamellated mechanoreceptor corpuscles in graft tissue. The only report known to us using electron microscopy (Goertzen et al, 1994) had to be retracted by the editors of the journal after thorough investigations (Fulford, 1997;Abbott, 1997).…”

Proprioception in anterior cruciate ligament deficient knees and its relevance in anterior cruciate ligament reconstruction

“…It has three components: a static awareness of joint position, awareness/detection of movement and acceleration, and a closed loop efferent activity which starts reflex response and regulates muscles. Proprioception is receptor and neural arc mediated; it has been demonstrated that a significant number of mechanoreceptors exist in the fibers of the ACL 4–8. These receptors (along with the mechanoreceptors located in the PCL, the collateral ligaments and capsular fibers), play an important role in the complicated neural network of proprioception 910.…”