Minimally Invasive Techniques for Foot Deformity Correction

Minimally Invasive Techniques for Foot Deformity Correction
Susan T. Mahan
Collin J. May
Insertion of Subtalar Extra-Articular Screw Arthroereisis for Treatment of Flexible Flatfoot in Children
Operative indications: Symptomatic flexible pes planovalgus and ankle pronation in an ambulatory child that has been recalcitrant to conservative methods of treatment (Figure 28.1).
  • Need dorsiflexion at least past neutral (ideally >20° past neutral when the foot is supinated and knee is extended)
    • Challenge the child preoperatively to obtain sufficient dorsiflexion using daily stretching and nighttime dorsiflexion boot
    • If not achieved, then should add Achilles lengthening (typically Vulpius type)
  • Age range in normal kids is typically 9 to 17 years
    • Most common age in normal children is 12 years
    • Ambulatory neuromuscular children with very severe pes planus can be treated as young as 6 years of age (almost always need Vulpius)
Equipment: Synthes 6.5-mm cannulated partially threaded screw (typically 30 mm for about 90% of patients). In very young (<10 years, or very small feet), the 4.5-mm cannulated system can be used. Smooth Kirschner wire (K-wire) (3/32 when using the 6.5-mm cannulated system). Schnitt or snap. Fluoroscopy.
Positioning: Supine with a bump under the hip so the leg sits naturally with patella forward. Tourniquet on involved limb. Sural nerve block.
Surgical Approach: The subtalar extra-articular screw arthroereisis (SESA) screw goes in through a small <1 cm incision just over the sinus tarsi on the anterolateral aspect of the foot. The SESA screw will go vertically in the calcaneus just distal to the isthmus; properly placed, it will impinge on the lateral talar process and lateral talus and prevent the talus from hyperpronation.
Techniques in Steps
  • If a Vulpius or other type of Achilles lengthening needs to be done, then that should be done first
  • Leg position during insertion
    • Very important!
    • Foot in neutral dorsiflexion and maximum supination (Figure 28.2)
    • Important to have patella forward (Figure 28.3)
    • Bump under the ankle/foot
  • Surgical incision
    • 5 to 8 mm lateral foot over sinus tarsi in Langer lines (Figure 28.4)
    • Spread down with snap or scissors to the sinus tarsi (Figure 28.5). If in correct place, will have 1 in of snap/scissors deep in the space (Figure 28.6)
  • Screw insertion
    • Large K-wire (3/32 fits through the 6.5-mm screw) placed first (Figure 28.7)
    • Starting point
      • Medial third of the calcaneal cuboid joint—about 1 cm medial from lateral edge of calcaneus
      • Just distal to the calcaneal isthmus
    • Trajectory
      • Press against the fibula with the wire
      • Aim a little anteriorly 15° to 20° and slightly medially—this angle is slightly forgiving if not perfect
      • Check fluoroscopy to confirm position of the guide pin (Figures 28.8 and 28.9)
    • Overdrill—just the near cortex—typically cannulated drill for 6.5-mm system (Figure 28.10)
    • Screw insertion (Figure 28.11)
      • Usually, Synthes 6.5-mm cannulated partially threaded screw
      • Length 3.0 cm in most all feet 90% to 95%
        • 3.5 in bigger feet
        • 2.5 in smaller feet
      • Confirm position of screw on fluoroscopy—anteroposterior (AP) and lateral (Figures 28.12 and 28.13)
      • Confirm clinically (Figure 28.14)
        • Weakest part of the procedure is how deep to put in the screw
        • Too proud will be undercorrected—needs to tuck under talus
        • Too deep will also undercorrect
        • When properly placed, can see screw head just under the skin level
        • Impinges on lateral talar process (cannot see this directly though)
  • Closure
    • Deep stitch
    • Skin
    • If no Achilles lengthening, then place soft dressing
    • If Vulpius done, then placed in solid short leg cast and may weight bearing in cast until follow-up
Postoperative Care
  • If no Vulpius and in soft dressing,
    • Non-weight bearing 3 days
    • First day post-op, patients are instructed to do 100 dorsiflexion eversion exercises
    • Follow-up day 3 to 5 for wound check
      • Exercises are also started
        • Skier exercises with feet apart and shift weight from one foot to the other—must have plantargrade stance (Figure 28.15)
        • Cannot weight bearing until 300 skier exercises