Lengthening of the Gastrocnemius-Soleus ComplexAn Anatomical and Biomechanical Study in Human Cadavers

Gregory B. Firth, MBBCh, FCS(Orth)SA, MMed(Orth), Michael McMullan, MPhil, FRCS(Tr&Orth), Terence Chin, MBBS,Francis Ma, MBBS, Paulo Selber, MD, FRACS, Norman Eizenberg, MBBS, Rory Wolfe, BSc, PhD,

and H. Kerr Graham, MD, FRCS(Ed), FRACS

Investigation performed at the University of Melbourne, Melbourne, Victoria, Australia

Background: Lengthening of the gastrocnemius-soleus complex is frequently performed for equinus deformity. Manytechniques have been described, but there is uncertainty regarding the precise details of some surgical procedures.

Methods: The surgical anatomy of the gastrocnemius-soleus complex was investigated, and standardized approacheswere developed for the procedures described by Baumann, Strayer, Vulpius, Baker, Hoke, and White. The biomechanicalcharacteristics of these six procedures were then compared in three randomized trials involving formaldehyde-preservedhuman cadaveric lower limbs. After one of the lengthening procedures was performed, a measured dorsiflexion force wasapplied across the metatarsal heads with use of a torque dynamometer. Lengthening of the gastrocnemius-soleuscomplex was measured directly, by measuring the gap between the ends of the fascia or tendon.

Results: The gastrocnemius-soleus musculotendinous unit was subdivided into three zones. In Zone 1, it was possibleto lengthen the gastrocnemius-soleus complex in either a selective or a differential manneri.e., to lengthen the gas-trocnemius alone or to lengthen the gastrocnemius and soleus by different amounts. The procedures performed in thiszone (Baumann and Strayer procedures) were very stable but were limited with regard to the amount of lengtheningachieved. Zone-2 lengthenings of the conjoined gastrocnemius aponeurosis and soleus fascia (Vulpius and Baker pro-cedures) were not selective but were stable and resulted in significantly greater lengthening than Zone-1 procedures (p