Medial Displacement Calcaneal Osteotomy (MDCO)

A medial displacement calcaneal osteotomy corrects a flexible hindfoot valgus by sliding the posterior tuberosity medially, which medialises the Achilles insertion and turns the Achilles from a deforming valgus force into a corrective one. It is a bony realignment that, on its own, addresses only one component of the deformity — so in practice it is almost always combined with soft-tissue and adjunctive bony procedures for stage II posterior tibial tendon dysfunction (PTTD). Primary indications - Flexible hindfoot valgus in stage II PTTD with preserved subtalar motion.

• Symptomatic flexible flatfoot with hindfoot valgus greater than 5-7 degrees on weight-bearing radiographs.
• Cavovarus correction using the lateralising (reverse) variant of the osteotomy.
• Combined reconstruction where medial column insufficiency and an Achilles valgus vector both need realignment. Concomitant procedures — almost always required - FDL transfer to the navicular or medial cuneiform (restores active inversion).
• Spring ligament repair or reconstruction (direct repair, graft augmentation or internal brace).
• Lateral column lengthening (Evans or Hintermann osteotomy) when forefoot abduction or lateral column shortening is present.
• Gastrocnemius or Achilles lengthening when an equinus contracture contributes to the deformity. The key surgical decision is therefore not whether to do an MDCO, but what to add to it:

Contraindications - Absolute: rigid hindfoot valgus (stage III or IV PTTD) with subtalar arthritis or fixed deformity — these require arthrodesis; active infection or ulceration over the lateral heel; severe peripheral vascular disease precluding safe wound healing.

• Relative: severe osteoporosis increasing nonunion risk; smokers who cannot cease nicotine peri-operatively; isolated hindfoot valgus without medial column pathology (rare — MDCO alone is seldom sufficient). Consent. Discuss sural nerve injury (5-15 percent), nonunion (3-8 percent), hardware prominence requiring removal (10-20 percent), under- or over-correction, wound complications, and the frequent need for concomitant procedures (FDL transfer, lateral column lengthening). Setup. Supine with a bump under the ipsilateral hip to internally rotate the leg, or lateral decubitus with the operative side up; the foot is placed at the end of the table to allow full ankle and subtalar motion. A thigh tourniquet is applied but rarely inflated. General or spinal anaesthesia with a popliteal or ankle block for post-operative analgesia (WALANT is not suitable for this bony procedure). Position a mini C-arm or image intensifier to obtain lateral, axial and Harris heel views intra-operatively, and confirm you can visualise the entire calcaneus and subtalar joint before prepping.

The goal: through a lateral oblique approach, expose the calcaneal body posterior to the peroneal tendons, cut the tuberosity obliquely at 45 degrees to the plantar surface (posterior and inferior to the posterior facet), translate the fragment 8-10 mm medially to medialise the Achilles insertion, and fix it with cannulated screws — almost always as part of a staged PTTD reconstruction. The exposure is laid out step by step below.

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Structures at risk in the lateral calcaneal approach

Rehabilitation | Phase | Timing | Immobilisation and loading | Rehabilitation | |-------|--------|----------------------------|----------------| | Immediate | 0-2 weeks | Below-knee splint or cast, non-weight-bearing; strict elevation for 48-72 hours | Wound review at 10-14 days; transition to a removable boot once the wound is stable | | Protected | 2-8 weeks | Touch weight-bearing in a boot from 2-6 weeks | Active ankle and subtalar range of motion from 2 weeks; radiographs at 6 weeks | | Progressive | 8-12 weeks | Gradual progression to full weight-bearing in orthotics by 10-12 weeks | Intrinsic and peroneal strengthening; custom medial-arch orthotics | | Return to activity | 3-6 months | Full weight-bearing in supportive orthotics | Low-impact activity from 3 months; running and sport from 4-6 months | Milestones and red flags - Milestones: 2 weeks — wound healed, in a boot, gentle range of motion; 6 weeks — radiographic evidence of early union, progress weight-bearing; 3 months — full weight-bearing with a near-normal gait.

• Red flags: increasing pain at the osteotomy site, wound breakdown, or new neurological symptoms — investigate promptly with imaging and clinical review. Most patients return to desk work by about 6 weeks and to heavy manual work by 12-16 weeks; full recovery of function is expected by 6-9 months in uncomplicated cases. Complications

Biomechanical rationale. Medial translation of the calcaneal tuberosity shifts the Achilles insertion medially, reducing its valgus moment arm and converting the Achilles from a deforming force into a corrective one. Cadaveric work shows that 8-10 mm of displacement corrects hindfoot valgus alignment and reduces medial column overload without significantly altering subtalar kinematics when combined with appropriate soft-tissue procedures; translation beyond about 12 mm adds medial soft-tissue impingement and wound tension without further corrective benefit. Clinical outcomes. Combined MDCO with FDL transfer and spring ligament reconstruction achieves good to excellent results in 75-85 percent of stage II PTTD patients at 5-10 year follow-up, with significant improvement in AOFAS scores, hindfoot alignment and patient-reported function. Isolated MDCO without addressing the posterior tibial tendon and spring ligament has higher failure rates and is not recommended. Nonunion and complication rates. Nonunion rates range from 2-8 percent in modern series with stable screw fixation; risk factors include smoking, diabetes and inadequate screw purchase. Sural nerve injury occurs in 5-15 percent when the nerve is not specifically protected. Hardware prominence requiring removal occurs in 10-20 percent of cases.