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Pes Planus / Flat Foot

- Discussion:
    - loss of normal medial longitudinal arch leads to pes planus, which can be flexible or rigid;
    - may arise as a consequence of hyper-pronation or from increased eversion of the subtalar joint;
           - hence, the calcaneus lies in valgus and external rotation relative to the talus;
    - associated midfoot sag may be due dorsal subluxation of the navicular on the talus;
           - talonavicular subluxation throughout stance phase is a major biomechanical consequence of the flat foot deformity;
    - the lateral column is short in relation to the medial column;
    - pediatric population:
           - typically infants have a minimal arch and often toddlers have flattening of the long arch, forefoot pronation, & heel valgus on
                    wt bearing, severity of which is variable (this is especially common in black children);
           - ligamentous laxity is apparent, & degree of abnormality in bone-ligament complex probably is determined genetically;
           - usually within the first decade, these children spontaneously develop a strong noraml arch;
           - references:
                  - The longitudinal arch. A survey of eight hundred and eighty-two feet in normal children and adults.  
                  - An investigation into the aetiology of flexible flat feet. The role of subtalar joint morphology

    - adult population:
         - may occur in 20 % of adults, most of which are flexible;
         - many people w/ flat foot can walk as comfortably and as easily as others who w/ normal arches as long as there is
                no heel cord contracture;
                - flat feet w/ a concomitant heel cord contracture may limit function;
         - there is some evidence that flat feet protect against metatarsal stress frx, but are poor shock absorbers with regard to the lower
                   back (causing higher incidence of low back pain);
                - in contrast, a cavus foot may actually be somewhat protective of stress related low back pain; 
         - etiology / cause of adult flat foot:
                - posterior tibial tendon rupture
                - deficiency of the spring ligament complex:
                       - Morphometric Dimensions of the Calcaneonavicular (Spring) Ligament 
                       - Spring Ligament Reconstruction Using the Autogenous Flexor Hallucis Longus Tendon
         - references:
                - The longitudinal arch. A survey of eight hundred and eighty-two feet in normal children and adults.  
                - Does arch height affect impact loading at the lower back level in running?    
    - how the subtalar joint affects flat feet:
    - associated conditions / diff dx:

- Clinical Manifestations:
    - must distinguish betwen flexible flat foot & rigid / spastic flat foot;
    - hypermobile foot:
         - the suspended foot will regain a normal appearing arch;
         - as the patient stands on his toes, the arch will reappear & heel will move out of a valgus position.
               - this is a good indirect test for nl subtalar motion;
    - forefoot varus:
         - once foot is placed in sub-talar neutral position assess whether there is relative forefoot varus (see exam of subtalar joint); 
    - defereniate between midfoot collapse and posterior tibial tendon insufficiency;
         - if patient can perform a single limb heel rise, then the posterior tibial tendon is functioning;
    - lateral impingement (sinus tarsi and fibular-calcaneal):
         - ref: Talocalcaneal and Subfibular Impingement in Symptomatic Flatfoot in Adults.
    - complicating factors:
         - heel cord contracture:
               - lateral deviation of achilles w/ wt bearing;
               - severe achilles contracture is associated with midfoot break down;
         - hyperpronation of hindfoot:
         - supination of the forefoot which does not correct when hindfoot is reduced;
         - everted heel w/ fails to invert w/ toe raise;
         - abducted forefoot;

- Radiographic Analysis:
     - standing lateral:
          - normally there is a straight line relationship between talus & first metatarsal;
          - in flat foot this relationship will be lost & there will be a sag at either the talonavicular or naviculocuneiform joint;
     - standing AP:
          - degree of heel valgus is important to assess;
          - talocalcaneal angle is measured and if > 35 deg, heel valgus is said to be present;
          - note the degree of talo-navicular uncoverage / subluxation;
     - oblique views to r/o tarsal colatition;
     - references:
          - Measurements on radiographs of the foot in normal infants and children

- Non Operative Treatment:
     - flexible flatfoot is generally a benign condition that rarely requires treatment;
     - heel cord stretching should be the main emphasis of treatment;
           - be sure to supinate the foot while stretching in order to "lock the midfoot" (avoids worsening midfoot collapse);
     - foot orthotics:
           - in most cases orthotics will not alter osseous relationships and are ineffective in may patients;
           - furthermore, arch supports may actually make the patient's symptoms worse, until a concomitant heel cord contracture is relieved;
           - in patients with talonavicular subluxation, consider taking a wt bearing AP of the patients feet with and without the inserts;
                 - if the talonavicular joint subluxation is not corrected w/ inserts then the inserts are probably not doing their job;
           - in some cases, patients with a calcaneovalgus deformity can "normalize their wt bearing pattern" w/ a medial heel wedge;
     - children and adolescents:
           - many feet improve as the child ages, at least until 5 to 6 yrs old;
           - flexible flatfeet are asymmetic for most pts, & its impossible to predict which planovalgus feet will become painful in adulthood;
           - hence, most orthopaedists consider their use to be unnecessary in children;
     - references:
           - Corrective shoes and inserts as treatment for flexible flatfoot in infants and children
           - The influence of footwear on the prevalence of flat foot. A survey of 2300 children.
           - The injury risk associated with pes planus in athletes. 
           - A Randomized Controlled Trial of Two Types of In-Shoe Orthoses in Children with Flexible Excess Pronation of the Feet  

- Indications for Surgery:
    - cerebral palsy:
           - equino-valgus foot deformities w/ heel cord contracture in patients w/ CP will generally tend to have break down of mid-foot and longitudinal arch;
           - these patients are best treated w/ tendo-achilles lengthening (w/ severe contracture) or a sub-talar fusion before mid-foot break down occurs;
                   - once mid-foot break down occurs, a triple arthrodesis is required;
    - painful rigid flatfoot:
           - small number of flexible flatfeet do not correct w/ growth & will become rigid due to adaptive changes occur;
           - painful rigid flat foot will require triple arthrodesis
    - painful flexible flatfoot:
           - in this situation, it is important to determine the anatomic cause of the pain;
           - as noted by Lau JTC and Daniels TR, a tarsal tunnel release w/ a concomitant pes planus may have the effect
                  of increasing posterior tibial nerve tension, which may explain the high rate of poor surgical results;
                  - in the same study, distraction calcaneo-cuboid arthrodesis reduced nerve tension;
           - reference:
                  - Effects of tarsal tunnel release and stabilization procedures on tibial nerve tension in a surgically created pes planus foot

- Contra-Indications for Surgery:
    - hyper-mobile joints (such as w/ Marfan's, Ehler's Danlos, Down's);
    - in adults, if feet are asymptomatic, surgery is almost never indicated;

- Operative Treatment:
    - medial os calcis sliding osteotomy or opening wedge osteotomy of lateral calcaneus may realign hindfoot & relieve
            symptoms w/o producing loss of motion associated w/ fusions;
    - FDL Transfer: (in the case of PT rupture);
    - medial calcaneal sliding osteotomy:
    - lateral column lengthening:
          - references:
                 - Effect of variation in calcaneocuboid fusion technique on kinematics of the normal hindfoot.  
                 - Selective tarsal arthrodesis: An in vitro analysis of the effect on foot motion.   
                 - Calcaneo-valgus deformity.    
                 - Early Graft Failure in Lateral Column Lengthening.
                 - Evans calcaneal lengthening procedure for spastic flexible flatfoot in 32 patients (46 feet) with a followup of 3 to 9 years.
                 - A Comparison of Lateral Column Lengthening and Medial Translational Osteotomy of the Calcaneus for Reconstruction of Adult Acquired Flatfoot
    - medial column fusion:
          - synthes medial column screw 
          - Isolated medial column stabilization improves alignment in adult-acquired flatfoot
          - The lateral column lengthening and medial column stabilization procedures.

    - medial cuneiform osteotomy:
          - may be indicated w/ fixed forefoot supination;
    - medial soft tissue reconstruction:
          - drill holes are made in the medial malleolus and the medial cuneiform thru which is passed a free tendon graft (using the EDL tendon);
          - ref: Reconstruction operations for acquired flatfoot: biomechanical evaluation.   
    - achilles tendon lengthening:
          - may be indicated for intractable equinus deformity, when other reconstructive procedures are to be performed as well;
    - triple arthrodesis:
          - indicated only when there is severe midfoot collapse; 
          - ref: Triple Arthrodesis With Lateral Column Lengthening for the Treatment of Planovalgus Deformity

Evaluation of hyperpronation and pes planus in adults.

Acquired flatfoot in adults.

Reconstruction with tenodesis in an adult flatfoot model. A biomechanical evaluation of four methods.

Calcaneal lengthening for valgus deformity of the hindfoot. Results in children who had severe, symptomatic flatfoot and skewfoot.

Dynamic support of the human longitudinal arch. A biomechanical evaluation.

The relationship of pes planus and calcaneal spur to plantar heel pain

The longitudinal arch. A survey of eight hundred and eighty-two feet in normal children and adults.   

The mechanics of the foot: II. The plantar aponeurosis and the arch.   

Two reconstructive techniques for flatfoot deformity comparing contact characteristics of the hindfoot joints

Isolated Medial Column Stabilization Improves Alignment in Adult-acquired Flatfoot.

Double arthrodesis in the adult. 

Diagnosis of Flexible Flatfoot in Children: A Systematic Clinical Approach

Flexible Flatfoot: Differences in the Relative Alignment of Each Segment of the Foot Between Symptomatic and Asymptomatic Patients