E-Journal

Orthotic Arch Height and Plantar Fasciitis                                                                  Issue No. 51

One of the most common conditions treated with foot orthoses is plantar fasciitis.  Repeated loading of the foot and excessive tension of the plantar fascia have been implicated by several authors as a cause of plantar fasciitis. Reducing tension in the plantar fascia is an important treatment objective for orthotic management of plantar fasciitis. Therefore, it is of great clinical interest to know whether the longitudinal arch support mechanism of foot orthoses have benefits with respect to the loading of the plantar fascia. Today's article will address this topic.

 

Sincerely,

 

Cherri Choate, DPM
Larry Huppin, DPM
Alona Kashanian, DPM  

Paul R. Scherer, DPM

Biomechanics of Longitudinal Arch Support Mechanisms in Foot Orthoses and their Effect on Plantar Aponeurosis Strain

The purpose of this investigation was to quantify the longitudinal arch support properties of several types of foot orthoses.

 

Methods

  • n = 7 cadaveric feet
  • Each specimen was tested under seven test conditions: barefoot, shoe only, shoe with five different foot orthoses (FO)
    •  Five foot orthoses tested:
      • Semirigid prefabricated
      • Soft custom, viscoelastic, semiweightbearing cast, no positive cast modifications
      • Semirigid cork custom, semiweightbearing cast, no positive cast modifications
      • Rigid functional Root-type custom, carbon composite (TL-61), standard neutral suspension cast
      • Rigid UCBL-type, carbon composite, partial weightbearing cast, no positive cast modification
  •  A transducer was surgically implanted in the plantar aponeurosis of each specimen to measure tension

Results

 

The results of this study showed that the UCBL, soft accommodative, and semirigid custom showed a significant reduction in strain within the plantar fascia. When the arch height of each orthosis was evaluated, it was found that the orthoses with the higher arch were more effective at reducing plantar aponeurosis strain.

Significance of the Article

 

This study suggests that orthoses with a higher arch and more acute arch angle were more effective at reducing strain within the plantar fascia than those with lower arches. Orthoses were less effective if they had a relatively flat medial surface or only a slight longitudinal contour and nominal arch height. The authors theorized that "to support the longitudinal arches of the foot effectively the medial surface contours of the orthosis must stabilize the apical bony structures of the foot's arch".

Significance for Orthotic Therapy

 

The results of this study imply that orthotic arch height is important in order to effectively decrease strain in the plantar aponeurosis. The problem with many functional orthoses prescribed for treating plantar fasciitis may not be their inherent design (as speculated by the authors), but that they are being manufactured with arches too low to adequately support the longitudinal arch and decrease tension on the plantar fascia.

 

Casting technique was noted as a critical aspect for achieving an orthosis that conforms to the arch of the foot. The authors note that the nonweightbearing (NWB) technique used in the study did not adequately capture arch height of the foot. This is not surprising since the technique described in this 1996 study is now considered antiquated. The current gold standard for NWB casting incorporates the application of a plantarflexory force to the first ray during casting. This results in a negative cast with a higher arch, matching the casting criteria recommended by the authors.

 

In addition to proper casting technique, plantar fascial tension can be further reduced by prescribing minimum cast fill to ensure that the orthoses conform tightly to the arch of the foot. Incorporating several degrees of inversion will further increase the arch height of the orthosis in the region of the talonavicular joint - the area of the foot noted in this study that needs support in order to provide optimum longitudinal arch control. 

 

The UCBL was a very effective device at reducing tension on the plantar fascia which may be due to the foot position being preserved with the higher heel cup and medial and lateral flanges. Based on this, it may be beneficial to prescribe functional orthoses with deeper heel cups and wider widths to further decrease plantar fascial tension. 

References

Kogler GF, Solomonidis SE, Paul JP. Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clin Biomech. 11(5):243-252, 1996

 
Additional
Resources
 

 

Follow-up Study 1999

 

NWB casting

  

UCBL

 

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