Collagen fibres and mechanoreceptors in regenerated menisci of rabbits

Does concomitant meniscectomy or meniscal repair affect the recovery of quadriceps function post-ACL reconstruction?

PURPOSE

The purpose of this study was to determine the effect of concomitant meniscal surgery on the recovery of quadriceps activation and strength at a time when individuals return to sport following anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty-six individuals that were cleared for participation following ACL reconstruction were invited to participate in this study. Participants were placed into groups according to surgical reports (ACL-only, n = 24; meniscal repair, n = 12; meniscectomy, n = 10). Quadriceps strength was quantified using isokinetic and isometric measures. Isokinetic strength was collected at 60°/s in concentric mode. Isometric strength was collected at 90° of knee flexion. Quadriceps activation was assessed using the burst superimposition technique and quantified via the central activation ratio. One-way ANOVAs were utilized to detect whether differences existed in quadriceps activation and strength between groups. Where appropriate, post hoc Bonferroni multiple comparison procedures were used.

RESULTS

Quadriceps activation (P = n.s.) and strength (isokinetic: P = n.s.; isometric: P = n.s.) were not different between groups.

CONCLUSION

Concomitant meniscectomy or meniscal repair did not affect the recovery of quadriceps activation and strength at a time when individuals return to sport following ACL reconstruction. Though group differences in quadriceps function were not detected, all participants demonstrated levels of quadriceps activation failure that are below healthy individuals at a time when they were returned to sport. Given that persistent quadriceps activation failure is detrimental to knee function, rehabilitation protocols that target quadriceps activation failure should be developed and employed post-reconstruction.

Mechanoreceptors in the Anterior Horn of the Equine Medial Meniscus: an Immunohistochemical Approach

Lameness due to stifle and especially meniscal lesions is frequent in equine species. In humans, mechanoreceptors involved in proprioceptive function are well studied. Given the high incidence of meniscal injuries in horses, and the lack of information concerning them in equine menisci, our objective was to study these corpuscles in six healthy anterior horns of the equine medial meniscus, which is the most common localisation reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against high molecular weight neurofilaments and glial fibrillary acidic proteins. From a purely fundamental point of view, our work highlights for the first time the presence of Ruffini, Pacini and Golgi corpuscles in equine meniscus. They were found, isolated or in clusters and always located at the vicinity of blood vessels, at the level of the anterior horn of the equine medial meniscus. This morphological approach could serve as a basis for clinical studies, to evaluate the impact of these corpuscles on the poor sportive prognosis in equine meniscal tears.

Anatomic double-bundle versus single-bundle ACL reconstruction: a comparative biomechanical study in rabbits

Thirty New Zealand white rabbits underwent anterior cruciate ligament (ACL) reconstruction in their right knees; 15 animals underwent a double-bundle anatomic ACL reconstruction using the medial third of the patellar tendon and the semitendinosus tendon. Additionally, 15 animals underwent ACL reconstruction, using a single-bundle semitendinosus tendon autograft. The knees of both groups were evaluated with a device similar to the KT1000 arthrometer onto which a dial indicator was attached (Mitutoyo dial indicator 2050) in 30 degrees and 90 degrees of flexion, preoperatively, after ACL resection and 3 months postoperatively. Statistical analysis of the results revealed that for 90 degrees of knee flexion, the mean estimated anterior shift for the double-bundle technique was 1.92 mm lesser than that of the single-bundle technique (P = 0.006). For 30 degrees of knee flexion, the mean anterior shift was again lesser than that of the single-bundle technique by 0.66 mm, but this difference was not statistically significant. The described double-bundle ACL reconstruction technique resulted in a more stable knee as far as the anterior tibial shift was concerned as compared to a single-bundle ACL reconstruction. This animal model may be potentially useful in the future for the study of other parameters influencing the outcome of the double-bundle ACL reconstruction.

Possible reflex pathway between medial meniscus and semimembranosus muscle: an experimental study in rabbits

Meniscus is a well innervated tissue with four types of receptors. These receptors are mainly concentrated at the anterior and posterior horns. Although they are intended to be a part in reflex arc, this function has not been thoroughly evaluated. We hypothesized that electrical stimulation of the normal meniscus would elicit electromyographic activity of the hamstring muscle via the reflex arc. Five adult domestic male rabbits were used in this study. Under general anesthesia, knee arthrotomy and thigh dissection were done to expose medial meniscus and semimembranosus muscle. Menisci were stimulated by Teflon-coated bipolar needle electrodes. Needles were placed in the posterior horn of the medial menisci. Two Teflon-coated monopolar needle electrodes were placed in semimembranosus muscle. A four-channel electromyograph was used for recording. Two different potentials were recorded from the target muscle. The first response had a very short distal latency and its amplitude was changing in accordance with the strength of the stimulus, suggesting that this response was being elicited by direct muscle stimulation. The second delayed response with less amplitude also appeared in some traces. The latency and the amplitude of this second response were fairly stable stating that this delayed response was being generated by a reflex pathway and seen in all subjects.

A prospective study on knee proprioception after meniscal allograft transplantation

The meniscus plays an important role in the proprioceptive ability of the knee joint. The aim of this prospective study was to assess the short-term influence of a meniscus replacement on the proprioception of the knee. Fourteen patients who had undergone a fresh meniscal allograft transplantation between May 2001 and June 2003 were tested pre-operatively and 6 months post-operatively. Disability regarding pain, stiffness and functionality of the affected knee during daily activities was measured by the Western Ontario and McMaster Universities Arthritis (WOMAC) scale. The knee joint position sense was assessed using the Biodex System 3 isokinetic dynamometer. The results of the WOMAC scale showed no significant differences concerning pain, stiffness or knee function between the pre- and post-operative condition of the knee. Assessment of the knee joint position sense at a reference point of 70 degrees of knee flexion revealed a significant improvement of the proprioception of the operated knee at 6 months after surgery compared with the pre-operative condition. The results of this study suggest that although no significant improvement of pain and functionality of the operated knee occurred at this short-term follow-up period, a meniscal allograft transplantation seems to have a significant positive effect on the joint position sense of the previously meniscectomised knee.

Influence of canine recombinant somatotropin hormone on biomechanical and biochemical properties of the medial meniscus in stifles with altered stability

OBJECTIVE

To determine biomechanical and biochemical properties of the medial meniscus in a semi-stable stifle model and in clinical patients and to determine the effect of canine recombinant somatotropin hormone (STH) on those properties.

ANIMALS

22 healthy adult dogs and 12 dogs with meniscal damage secondary to cranial cruciate ligament (CCL) rupture.

PROCEDURE

The CCL was transected in 15 dogs, and stifles were immediately stabilized. Implants releasing 4 mg of STH/d were placed in 7 dogs, and 8 received sham implants. Seven dogs were used as untreated controls. Force plate analysis was performed before surgery and 2, 5, and 10 weeks after surgery. After 10 weeks, dogs were euthanatized, and menisci from surgical and contralateral stifles were harvested. The torn caudal horn of the medial meniscus in dogs with CCL rupture comprised the clinical group. Creep indentation determined aggregate modulus (HA), Poisson's ratio (v), permeability (k), and percentage recovery (%R). Water content (%W), collagen content (C), sulfated glycosaminoglycan (sGAG) content, and collagen type-I (cI) and -II (cII) immunoreactivity were also determined.

RESULTS

Surgical and clinical groups had lower HA, k, %R, C, sGAG, cI, and clI and higher %W than the non-surgical group. Surgical stifles with greater weight bearing had stiffer menisci than those bearing less weight. Collagen content was higher in the surgical group receiving STH than the surgical group without STH.

CONCLUSIONS AND CLINICAL RELEVANCE

Acute stabilization and moderate weight bearing of the CCLdeficient stifle appear to protect stiffness of the medial meniscus. Normal appearing menisci from CCL-deficient stifles can have alterations in biomechanical and biochemical properties, which may contribute to meniscal failure.

Function of the normal meniscus and consequences of meniscal resection

The principal functions of the meniscus are load transmission and shock absorption, based on the meniscal collagen architecture, the biochemical fluid composition, and the proteoglucan-collagen meshwork. The mobile menisci transmit 50-90% of load over the knee joint, depending on knee flexion angle, femoral translation and rotation. The meniscus contributes to knee joint proprioception and probably also to joint stability. Late consequences of total and partial meniscectomy are radiographic osteoarthritis, with a varying percentage of these patients having symptoms. Malalignment, concomitant articular cartilage lesions, and ligament instability are absolute risk factors, while age, lateral compartment, and continued sport activity are relative risk factors. Acute reinsertion of meniscal tears in the red-red or red-white zones can be performed successfully by arthroscopic technique. Also in chronic tears stable healing can be expected in most cases, if the scar tissue is resected.

Meniscal regeneration or meniscal transplantation?

Owing to the initial necrosis to which any freely transplanted biological graft is subjected, meniscus transplantation is based on similar principles to meniscal regeneration. Both methods rely on repopulation of extrinsic cells of the graft. In the former procedure a biological matrix (meniscus, tendon, fatpad) is used as graft (scaffold), whereas in meniscal regeneration commercially available resorbable or non-resorbable scaffolds are implanted. However, the cellular (re)population and (re)vitalization process is deleterious rather than beneficial for the function of the graft as the remodelling of the tissue leads to shrinkage and narrowing of the implant. In addition, improper fixation and subsequent elongation of the anterior and posterior bony attachments leads to peripheral graft dislocation, loss of the load distribution function, and subsequently to cartilage degeneration. Hence, meniscus transplantation or regeneration faces two major problems: 1) remodelling of graft to inferior tissue properties after allograft transplantation, or lacking establishment of normal tissue properties after use of biological matrixes other than the meniscus (fatpad, tendon), or commercially available matrixes; 2) improper fixation with elongation of the anterior and posterior attachments. Furthermore, use of allografts incorporates the risk for disease transmission. Today we are unable to control these problems, and therefore the concept of meniscal replacement does not work yet. Further research is necessary to control remodelling and improve fixation to make this procedure a successful one in the future.

Neural and vascular anatomy of the menisci of the human knee

STUDY DESIGN

Review of literature.

OBJECTIVES

To review the general anatomy, vascular anatomy, healing potential, neural anatomy, and sensory functions of the menisci of the human knee.

BACKGROUND

Recent research has revealed important roles and functions of the menisci of the human knee.

METHODS AND MEASURES

A Medline search was performed using the following title and key words: menisci, meniscus, meniscal, vascular, blood, neural, nerve, anatomy, healing, sensory, mechanoreceptors, proprioception, nociceptors, surgery, meniscectomy, repair, and rehabilitation. The references from each article obtained were then reviewed in order to find additional articles not already located through the Medline search.

RESULTS

In adults, the blood supply to the menisci of the knee reaches the outer 10% to 33% of the body of the menisci. This portion of the menisci is capable of inflammation, repair, and remodeling. Neural innervation with nociceptors and type I, II, and III mechanoreceptors reaches the outer 66% of the body of the menisci. The anterior and posterior horns of the menisci have a rich supply of both blood vessels and nerves.

CONCLUSIONS

The menisci of the human knee are an important source of proprioceptive information regarding the position, direction, velocity, and acceleration and deceleration of the knee. Rehabilitation following injury or surgery to the menisci of the knee should, therefore, incorporate a proprioceptive retraining program that respects both the abilities and inabilities of different portions of the menisci to follow through with repair and remodeling.