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Is Plantaris a sensory muscle or a vestigial muscle?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by caseytm99, Feb 13, 2007.

  1. caseytm99

    caseytm99 Member

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    Your friendly podiatrist, Mike

    I am currently reviewing literature on neurological studies which incorporate concentrations of muscle spindles, golgi tendon organs and other proprioceptors within lower limb muscles. The high concentrations within the Plantaris muscle compared to its size and also with comparison to lower concentrations in soleus and gastrocnemius in humans seems to point towards the Plantaris as being a sensory muscle providing regular constant information in a variety of signals which would assist movement within the muscles of the triceps surae group. There is experimental evidence which supports this view, and that the Plantaris muscle is not an evolutionary atrophied muscle from the past in humans. Evolutionists who support that the plantaris is a vestigial muscle base their claims on assumption and supposition which is backed by evidence from quadropeds and no studies of bipeds with regards to this. Surgeons readily take the plantaris tendon for replacement surgery, thinking that it no longer has a mechanical role and is of no functional benefit but there has been no studies at all which they can base this assumption on. Studies are needed both for the mechanical and sensory role for a conclusion to be drawn. I suggest that with the new understanding of parallel muscle combinations and sensory muscle investigations, that the Plantaris is actually the 'brain' of the triceps surae group from a controlling point of view. This would indeed have some impact on biomechanics and proprioception within the leg.

    Any thoughts on this subject?
  2. I have noted no change in biomechanical function or proprioceptive ability of the numerous patients that I have seen over the past two decades who have had either plantaris rupture or plantaris tendon excision for tendon repair. Your suggestion that the plantaris is the "brain of the triceps surae" is not supported by any clinical evidence or research that I know of, your suggestion does not make good physiological sense and your suggestion will probably be met with resistance from any intelligent biomechanist, physiologist, orthopedic surgeon or podiatrist.

    Good luck in your quest. :eek:
  3. David Smith

    David Smith Well-Known Member

    Dear Caseytm99

    Sounds interesting

    Can you reference this experimental evidence?
    Is there any evidence that the 6 to 7% of subjects with plantaris missing suffer any problems in gait due to reduced proprioception.

    Ref: Journal of Bone and Joint Surgery, 1943;25:822-827.
    © 1943 by The Journal of Bone and Joint Surgery, Inc

    An Anatomical Study of 750 Specimens
    Edward H. Daseler M.S. M.D.1 and Barry J. Anson PH.D.1
    1 Northwestern University Medical School, Chicago

    The plantaris muscle and tendon may be regarded as the vestigial remains of a primitive flexor muscle of the toes, which, originally continuous with the plantar aponeurosis, later was rendered discontinuous through intermediate attachment to the calcaneum.

    The plantaris muscle and its tendon are subject to considerable variation in both the points of origin and of insertion. In an examination of 150 lower extremities, the authors have encountered four types of insertion of the tendon.

    In 750 consecutive lower extremities examined by the present authors, the plantaris muscle was absent in fifty (6.67 per cent.). In one-third of the specimens in which the muscle was missing, the absence was bilateral.

    The surgical utilization of the plantaris tendon is particularly indicated as a desirable substitute for the fascia lata in hernial repair, tendon transplants, and repair of ligaments.

    Other studies were referenced which all show the same 6 - 7% agenesis of plantaris was found.

    Cheers, Dave
  4. caseytm99

    caseytm99 Member

    I have read the following referenced papers in which there seems to be supported evidence of experimental detail with regards to parallel muscle combinations where the smaller muscles influence the larger muscles activity. I'm still reviewing even more literature on the matter.

    Ref: Comparison of Muscle Spindle Concentrations in Large and Small Human Epaxial Muscles Acting in Parallel Combinations
    AJ Nitz, D Peck. The American Surgeon May 1986

    Ref: A Comparison of Spindle Concentrations in Large and Small Muscles Acting in Parallel Combinations.
    D Peck, DF Buxton, AJ Nitz. Journal of Morphology 180-243-252 (1984)

    The Plantaris and the Question of Vestigial Muscles in MAn
    DN Menton,. CEN Technical Journal 14(2) 2000
  5. Casey:

    If the plantaris muscle is so important, then why don't patients that have had the plantaris tendon resected for use elsewhere in the body not seem to have any functional deficits as a result? :confused: :eek:
  6. caseytm99

    caseytm99 Member

    I agree that the removal of the plantaris does not apparently affect the function of the triceps surae group, but I am looking for published empirical evidence to support this, since I'm producing a literature review, and I can't find any...yet.

    It seems that both Gastrocnemius and Soleus have enough muscle spindle golgi tendon organ concentrations to function adequately without plantaris, but a simple measurable experiment using the latest technological tools on sample patients before and after plantaris excision should prove this. Might cost too much though....

  7. Mike:

    Your basic premise that loss of plantaris will somehow affect the ability of the central nervous system to function during weightbearing activities makes no sense. I was an animal physiology major before entering podiatry school and even in those days of nearly 30 years ago the complexity of the interactions between afferent and efferent messages of the CNS were understood at a level that would make your argument seem ridiculous. Maybe if you could produce one shred of evidence showing that the plantaris is the "brain of the triceps surae", then I would believe you. Until that time, it seems to me like you are trying to construct a building on foundation of quicksand.
    Last edited: Mar 10, 2007
  8. David Smith

    David Smith Well-Known Member

    Hi! Casey99

    Oh if only they were :)

    Mike, The more you learn the less you know eh!

    Do you think that there may be quite a lot of redundancy in this system that can run quite well with or without the plantaris.
    Maybe the plantaris is an important sensory muscle in the horse or bear and hasn't lost its sensory organs in the human even though the muscle is vestigal and its proprioceptive input is not important. (Just guessing)
    So assume that there are many more sensory organs in plantaris relative to its size than other muscles. Soleous and gastroc give lets say 1000 units of transmission (T) information to the CNS, plantaris gives 2000 units of (T)information to the CNS.
    One might assume the plantaris is very important to the total input of information to the CNS. But this may not be so, Assume that gastroc and soleous give information that has a magnitude (M) of 10000 units but plantaris gives information with a magnitude (M) of 5 units.
    Do the math T x M (did I just say math, Bloomin American influences) 2000 x 5 = 10000 (10^4) compared to 1000 x 10000 = 10,000,000 (10^7).

    In other words plantaris shouts alot but hasn't got much to say. The CNS pretty much ignores its input.

    This is just a suggestion but misinterpretation of data in this way is easily done in research if not careful.

    All the best Dave
  9. HansMassage

    HansMassage Active Member

    My observation is that it dose shout a lot but just gets ignored. My antalgic posture clients often have tender origin and insertion tenderness and yes the those points do very from one client to the next.

    Unilateral tenderness with a functional shortening of one leg and excessive supination at foot strike excessive pronation at push off seems to be the pattern.

    I have learned to listen to it personally to avoid more severe symptoms. Most clients have no idea it even exists and ignore its message until I put my finger on it.

    By the way the positional release is flexion of the knee with external rotation and planter flexion of the ankle with pronation of the fore foot. Ankle flexion usually improves after release.

    Hans Albert Quistorff, LMP
    Antalgic Posture Pain Specialist

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