CHAPTER SYNOPSIS:

Tendon transfers about the foot and ankle aim to restore muscular balance within a maloriented foot with the ensuing functional disorders. A deficient tibial posterior tendon will cause insufficient mid-foot suspension and lead to painful arthritis. Flexor digitorum longus tendon transfer is considered the most valuable tendon to compensate for the lack of power of the posterior tibial tendon.

IMPORTANT POINTS:

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  Assessment of orientation and alignment of the weight-bearing foot and ankle.

  
  
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  Extrinsic musculature is responsible for preserving orientation of the osteoarticular structures.

  
  
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  Those muscles are:

  
  
  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Triceps surae	TS
  Flexor hallucis longus	FHL
  Flexor digitorum longus	FDL
  Tibialis posterior	TP
  Tibialis anterior	TA
  Extensor hallucis longus	EHL
  Extensor digitorum longus	EDL
  Peroneus tertius	P3
  Peroneus brevis	PB
  Peroneus longus	PL

   
  
  

Indications:

Contraindications for tendon transfers about the foot are fairly generic to most major foot reconstructions:

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  Vascular impairment of the soft tissues

  
  
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  Lack of muscular strength and function

CLINICAL/SURGICAL PEARLS:

Indications

• 1
  

  Congenital posterior tibial tendon deficiency with painful flatfoot. Pain is located on the insertion of the tendon and/or at the sinus tarsi. Pain at the first location (medial) is due to the strong pull on the tendon causing fatigue entesopathy, and the second location (lateral) is due to the secondary bony impingement between the processus lateralis tali and the Gissane’s angle on the calcaneus.

  
  
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  Degenerative posterior tibial tendon deficiency with secondary flatfoot. Pain is located in the noninsertional section of the tendon. It is usually of insidious origin, but there might be a traumatic event that leads to increasing symptoms.

  
  
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  Metabolic tendon diseases—examples are polyarthritis and hyperuricemia. The tendon undergoes structural degeneration and provokes pain and successive tears ending in degenerative flatfoot deformity.

CLINICAL/SURGICAL PITFALLS:

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  Tendon transfers may overcorrect the desired aim of the reconstruction. It is essential to evaluate the point of insertion when transferring the tendon.

VIDEOS AVAILABLE

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Indications for tendon transfers about the foot and ankle are multiple. As in the upper limb, functional movement prevails in surgical reconstruction; in the lower limb, equilibrated forces transmitted on a functionally well-oriented foot is of mandatory importance. In case of muscular imbalance, one aims at restoring the equilibrium by transferring tendon and muscle function. In case of a pathology of the tendon, one aims at restoring function by transferring the tendon while the original muscle still prevails in its function. Two clinical situations of this kind are clinically relevant—the chronic tendinopathy of the heel cord and of the posterior tibial tendon. The heel cord can be well substituted by the flexor hallucis longus muscle, which acts as a muscle flap to a hypovascularized region, while the posterior tibial tendon can be substituted for by the flexor digitorum longus tendon. In both cases the primary muscle still plays the most important role. In this chapter, we discuss the technique of flexor digitorum longus (FDL) transfer for posterior tibialis tendon pathology.

Posterior tibial tendon deficiency (PTTD) has been described many times in the past, but comprehensive understanding of causes and consequences of this pathologic entity is not yet part of general orthopedic teaching. With chronic tendon deficiency, one can either propose tendon repair or substitution as treatment options. Considering substitution of the tendon, the anatomy offers 10 muscles of the lower leg with extending tendons to the foot.

Normal function of the extrinsic musculature can be evaluated within the sagittal plane (flexion-extension) and frontal plane (supination-pronation). In normal feet, the flexors are always more powerful than the extensors. The same is true for the supinators versus the pronators.

Substitution of pathologic tendons through tendon transfers represents the most biological way of functional reconstruction. An occasional gain in motion is secondary. Any surgical procedure including muscle tendon transfers should be preceded by a precise “mapping” of all extrinsic musculature about the foot and ankle. Best investigation could include special evaluation by a neurologist with eventual electromyography.

Best indications for tendon transfers include:

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  Neuropathy (Charçot-Marie-Tooth)

  
  
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  Neuromuscular diseases (cerebral palsy)

  
  
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  Peroneus palsy

  
  
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  Club foot deformity

  
  
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  Amputations (trauma, diabetes)

  
  
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  Hammer toes

  
  
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  Posterior tibialis tendon pathology (flat feet)

  
  
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  Stabilization of axial corrections (osteotomies, fusions)

In this context, PTTD is either congenital, which can be asymptomatic (flat feet), or acquired, which might be based on some congenital traits with subsequent decompensation or trauma, including repetitive microtrauma. Secondary tendinopathy occurs regularly in immunologic (polyarthritis) and metabolic (gout) diseases.

CLASSIFICATION SYSTEM

A classification system has value if it has direct implications to treatment and, in this case, to the adequate surgical procedure. In PTTD, the clinical picture is dominated by pain, functional impairment of gait, and the development of secondary arthritis. A logical classification has been proposed in the past. Based on this classification, there are three major stages of the pathology:

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  Painful chronic inflammation and morphologic alterations of the posterior tibial tendon

  
  
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  Chronic tendonitis with alteration of the osteoarticular orientation of the hindfoot.

  
  
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  Chronic tendonitis with secondary arthritic alteration of the talocalcaneonavicular joint