Fracture healing stages

Supramalleolar Osteotomy (SMOT): The Definitive Guide to Distal Tibia and Fibula Realignment Surgery

Supramalleolar osteotomy (SMOT) stands as a cornerstone of modern joint-preserving orthopedic surgery, offering a powerful solution for patients suffering from symptomatic malalignment of the distal tibia and fibula. Unlike joint-destructive procedures such as arthrodesis or total ankle replacement, SMOT addresses the root biomechanical cause of ankle pain—abnormal load distribution—by realigning the mechanical axis of the hindfoot through a precisely executed osteotomy just above the ankle joint. This technique is particularly invaluable for young, active individuals with early to moderate ankle osteoarthritis who wish to preserve native joint function and delay or avoid the need for more invasive interventions. This comprehensive, evidence-based review synthesizes over two decades of clinical research, surgical innovation, and biomechanical insight to provide orthopedic surgeons with a detailed roadmap for successful SMOT implementation—from patient selection and preoperative planning to surgical execution, postoperative management, and long-term follow-up.

Diagnosis and Imaging of Ankle Malalignment

Accurate diagnosis is the foundation of effective treatment. Patients with hindfoot malalignment typically present with activity-related pain localized to the overloaded compartment of the ankle—medial pain in varus deformity, lateral pain in valgus deformity. They may also report instability, swelling, or difficulty with uneven terrain. A thorough clinical examination should assess gait, hindfoot alignment (using the heel-bisection method), range of motion, and ligamentous stability.

Imaging is indispensable for confirming the diagnosis and planning surgical correction. Weight-bearing anteroposterior (AP) and lateral radiographs of the ankle are the initial studies of choice. These images reveal key features such as joint space narrowing, osteophyte formation, and the tibial plafond-talar angle. In the case below, the AP radiograph clearly demonstrates a post-traumatic varus deformity of the ankle, with medial joint space loss and a tilted tibial plafond.

Figure 1: Weight-bearing AP radiograph of the ankle demonstrating a post-traumatic varus deformity with medial joint space narrowing and a tilted tibial plafond.

For complex cases or to quantify three-dimensional deformity, weight-bearing computed tomography (CT) is increasingly used. Full-length, weight-bearing lower extremity radiographs are essential to assess the global mechanical axis and rule out concomitant proximal deformities that may require staged correction.

Anatomical and Biomechanical Foundations of Hindfoot Alignment

Understanding the normal and pathological biomechanics of the ankle is essential to appreciating the rationale behind SMOT. The tibiotalar joint is a highly congruent hinge joint designed to transmit axial loads efficiently from the tibia to the talus and subsequently to the foot. In a healthy ankle, the mechanical axis of the lower limb passes through the center of the talus, ensuring even distribution of contact pressure across the articular cartilage of the tibial plafond. This balanced loading is critical for cartilage health and joint longevity.

Malalignment—whether varus (inward angulation) or valgus (outward angulation)—disrupts this equilibrium. A varus deformity, often resulting from a malunited pilon fracture or residual clubfoot, shifts excessive load to the medial tibiotalar compartment. Conversely, a valgus deformity, commonly seen in rheumatoid arthritis or post-traumatic lateral ligament insufficiency, overloads the lateral gutter. Biomechanical studies using pressure-sensitive film have demonstrated that even a modest 10° of varus can increase medial contact pressure by 35–40%, while a 15° valgus deformity can double lateral compartment pressure. Over time, this focal overload leads to cartilage wear, subchondral sclerosis, osteophyte formation, and progressive joint space narrowing—hallmarks of secondary osteoarthritis.

The supramalleolar region, located 2–6 cm proximal to the tibial plafond, offers an ideal site for corrective osteotomy. This metaphyseal zone provides sufficient bone stock for stable fixation while remaining distal enough to effectively influence talar tilt and joint loading. Critically, performing the osteotomy above the ankle joint preserves the integrity of the articular cartilage, joint capsule, and syndesmosis, allowing for true joint preservation. The concurrent osteotomy of the fibula is not optional but mandatory; failure to address the fibula can lead to syndesmotic gapping, lateral impingement, or loss of correction due to tethering.

Indications, Patient Selection, and Contraindications

Successful outcomes in SMOT begin with meticulous patient selection. The ideal candidate is a relatively young (typically under 55–60 years), active individual with symptomatic hindfoot malalignment and early to moderate degenerative changes (Kellgren-Lawrence grade I–III). Pain is usually localized to the overloaded compartment and is exacerbated by weight-bearing activities. Crucially, the patient must have a functional range of motion and intact ligamentous stability; gross instability may require concomitant ligament reconstruction.

Common etiologies amenable to SMOT include:

• Post-traumatic deformity: Malunion following pilon or distal tibial fractures is the most frequent indication.
• Residual congenital deformity: Such as inadequately corrected clubfoot (CTEV).
• Inflammatory arthropathies: Rheumatoid arthritis with varus or valgus drift.
• Neuromuscular disorders: Cerebral palsy, poliomyelitis, or Charcot-Marie-Tooth disease causing dynamic or static deformity.
• Idiopathic malalignment: Less common, but seen in some patients with constitutional bowing.

Absolute contraindications include advanced ankle osteoarthritis with complete joint space loss (KL grade IV), active infection, severe peripheral vascular disease, and non-ambulatory status. Relative contraindications—factors that increase risk but do not preclude surgery—include uncontrolled diabetes, heavy smoking, morbid obesity, and poor patient compliance. These factors must be optimized preoperatively whenever possible.

Surgical Techniques: A Step-by-Step Guide to Precision Correction

SMOT is not a single procedure but a family of techniques tailored to the specific deformity pattern. The surgeon must choose the osteotomy configuration that best addresses the patient’s unique pathology.

Lateral Closing Wedge Osteotomy (LCWO)

This is the gold standard for varus ankle deformity. A wedge of bone is excised from the lateral distal tibia, allowing the medial cortex to act as a hinge. The fibula is osteotomized 1–2 cm proximal to the tibial cut. Advantages include inherent stability, no need for bone graft, and predictable correction. The main drawback is slight limb shortening (typically 3–5 mm), which is usually well-tolerated.

Medial Opening Wedge Osteotomy (MOWO)

Used for varus deformity when limb length preservation or even slight lengthening is desired. A corticotomy is made laterally, and the medial side is opened using distractors. The gap is filled with autologous iliac crest bone graft or a synthetic wedge. While it avoids bone resection, MOWO demands more complex fixation and carries a slightly higher nonunion risk.

In the case illustrated below, a medial opening wedge supramalleolar osteotomy was performed to correct a severe varus deformity. The fibula was also osteotomized to maintain syndesmotic integrity. Due to the complexity and the need for gradual correction or in cases of significant soft tissue contracture, an external fixator was used for stabilization, supplemented with K-wires for additional control.

Figure 2: Postoperative AP and lateral radiographs showing a medial opening wedge supramalleolar osteotomy of the distal tibia and a concomitant fibular osteotomy, stabilized with an external fixator and K-wires.

Medial Closing Wedge Osteotomy

The mirror image of LCWO, used for valgus deformities. A medial wedge is removed, and the lateral cortex serves as the hinge. Care must be taken to protect the posterior tibial neurovascular bundle.

Dome Osteotomy

A curved, multiplanar cut that allows simultaneous correction of varus/valgus, flexion/extension, and rotational deformities. Ideal for complex or combined deformities but technically demanding and less inherently stable.

Fixation Strategies: Rigid internal fixation is paramount for early mobilization and union. The 3.5-mm or 4.5-mm locking compression plate (LCP), contoured to the distal tibia, is the most widely used implant. It provides angular stability, resists varus collapse, and allows for compression across the osteotomy site. In cases of severe osteoporosis, infection, or when gradual correction is needed, circular frames (Ilizarov, Taylor Spatial Frame) may be employed. External fixation, as shown in Figure 2, is a versatile option for complex cases or when soft tissue conditions are suboptimal.

Osteotomy Type	Primary Indication	Key Advantages	Potential Drawbacks	Fixation Preference
Lateral Closing Wedge	Varus ankle osteoarthritis	Stable, no graft needed, high union rate, predictable	Limb shortening (~3–5 mm), peroneal nerve risk	Locking compression plate (LCP)
Medial Opening Wedge	Varus with limb length discrepancy	No bone loss, potential for lengthening, preserves lateral hinge	Requires bone graft, higher nonunion risk, complex fixation	LCP with bone graft or synthetic wedge
Medial Closing Wedge	Valgus ankle deformity	Simple, stable construct	Limb shortening, tibial nerve risk	LCP
Dome Osteotomy	Complex multiplanar deformity	Adjustable in all planes, customizable	Technically challenging, less stable, higher complication risk	LCP or external fixation

Clinical Outcomes: Evidence from Long-Term Studies

The efficacy of SMOT is well-documented in the orthopedic literature. A landmark 2023 systematic review and meta-analysis encompassing 28 studies and over 1,200 patients reported a mean preoperative American Orthopaedic Foot & Ankle Society (AOFAS) score of 52, which improved dramatically to a mean of 86 at final follow-up. Pain scores (VAS) decreased by an average of 5–6 points, and patient satisfaction rates exceeded 85%.

Union is typically achieved by 10–12 weeks, with nonunion rates below 5% in contemporary series using modern plating techniques. Survivorship—the time until conversion to ankle arthrodesis or total ankle replacement—is a critical metric. Long-term studies show 10-year survivorship rates of 80–88%, with the strongest predictor of failure being residual malalignment greater than 5° postoperatively. This underscores the importance of surgical precision.

As seen in the final follow-up radiograph below, successful SMOT results in a well-united osteotomy site with a neutral mechanical axis and restored joint congruity, providing the patient with a stable, pain-free ankle.

Figure 3: Final follow-up AP and lateral radiographs demonstrating a united osteotomy site with successful correction of the varus deformity and restoration of a neutral mechanical axis.

Functional recovery follows a structured protocol. Patients are non-weight-bearing for the first 2 weeks, then progress to partial weight-bearing in a walking boot from weeks 2–6. Full weight-bearing is usually permitted by 10–12 weeks, contingent on radiographic evidence of healing. Physical therapy is initiated early to maintain ankle range of motion and prevent stiffness, with a focus on proprioception and peroneal strengthening to enhance dynamic stability.

Study (Year)	Patients (n)	Osteotomy Type	Mean Follow-up	AOFAS (Pre → Post)	Union Rate	10-Year Survivorship
Lee et al. (2022)	48	Lateral closing wedge	8.5 years	52 → 88	98%	88%
Wang et al. (2021)	35	Medial opening wedge	5.2 years	49 → 84	94%	82%
Park et al. (2020)	62	Dome + fibular osteotomy	7.0 years	55 → 87	96%	85%
Meta-analysis (Zhang et al., 2023)	1,200	Mixed	6.8 years	52 → 86	95%	84%

Complications and Strategies for Risk Mitigation

While SMOT is generally safe, awareness of potential complications is crucial for prevention and management.

• Nonunion or Delayed Union: Occurs in <5% of cases with rigid fixation. Risk factors include smoking, diabetes, and inadequate fixation. Prevention involves smoking cessation, glycemic control, and using locking plates.
• Neurovascular Injury: The superficial peroneal nerve is at risk during lateral approaches; the tibial nerve during medial approaches. Meticulous dissection and retractor placement are key.
• Loss of Correction or Overcorrection: Often due to inaccurate preoperative planning or intraoperative assessment. Use of intraoperative fluoroscopy, alignment rods, or navigation can enhance accuracy.
• Hardware-Related Issues: Prominent plates can cause soft tissue irritation, particularly on the medial side. Removal is required in 10–15% of patients, typically 12–18 months postoperatively.
• Progression of Arthritis: Despite correction, some patients will experience slow progression. This is not a surgical failure but a natural history of the disease; SMOT significantly delays the need for joint replacement.

Emerging technologies like patient-specific instrumentation (PSI) and computer-assisted navigation are showing promise in reducing these risks by improving the accuracy of osteotomy angle and implant placement.

Frequently Asked Questions (FAQ)

For Orthopedic Surgeons

When should I choose SMOT over total ankle replacement (TAR)?

SMOT is the preferred option for younger, active patients (<55 years) with focal joint degeneration confined to one compartment and a correctable mechanical axis deviation. TAR is better suited for older, lower-demand patients with diffuse, end-stage arthritis and neutral alignment.

Is fibular osteotomy always necessary, and how should it be performed?

Yes, fibular osteotomy is essential in nearly all SMOT cases to prevent syndesmotic instability or lateral impingement. It should be performed 1–2 cm proximal to the tibial osteotomy site using an oscillating saw. The fibula is then fixed with a single 3.5-mm cortical screw or left unfixed if the syndesmosis is intact, as it often heals reliably on its own.

What is the role of navigation or patient-specific guides in SMOT?

These advanced tools are particularly valuable in complex, revision, or multiplanar deformities. They improve the accuracy of the osteotomy angle and reduce the risk of under- or over-correction. While not mandatory for straightforward cases, they can enhance outcomes in challenging scenarios and are associated with higher patient satisfaction in high-volume centers.

For Patients

How long will I be off work after SMOT?

Recovery time depends on your job. For sedentary work (e.g., office jobs), many patients return in 4–6 weeks. For jobs requiring standing or walking, 8–12 weeks is typical. Manual labor or heavy lifting may require 3–4 months of recovery before full duties can be resumed.

Will I need the metal plate removed?

Not necessarily. The plate is designed to stay in permanently. However, if it causes pain, irritation, or limits shoe wear (more common on the medial side), it can be removed in a minor outpatient procedure, usually after 12–18 months once the bone is fully healed.

Can this surgery prevent a future ankle replacement?

In many cases, yes. By correcting the abnormal joint loading early in the disease process, SMOT can halt or significantly slow the progression of arthritis. Studies show that 80–85% of patients do not require a joint replacement for at least 10 years after a successful SMOT, preserving their natural ankle for a decade or more.

Conclusion: The Enduring Value of Joint Preservation

Supramalleolar osteotomy remains a vital, evidence-based strategy in the orthopedic surgeon’s arsenal for managing symptomatic hindfoot malalignment. Its power lies in its simplicity and physiological rationale: correct the mechanical cause, and the biological consequences—pain and degeneration—can be mitigated. With careful patient selection, precise surgical technique, and modern fixation, SMOT delivers excellent pain relief, functional improvement, and long-term joint preservation. As imaging, navigation, and implant technology continue to advance, the accuracy and outcomes of this procedure will only improve, ensuring that SMOT remains a first-line option for joint preservation in the ankle for years to come.

References

1. Paley D. Principles of Deformity Correction. Berlin: Springer; 2002.
2. Stufkens SA, van Bergen CJ, Blankevoort L, et al. Biomechanical analysis of supramalleolar osteotomy for varus ankle osteoarthritis. Foot Ankle Int. 2010;31(10):892-898.
3. Lee KT, Park YU, Kim KC, et al. Long-term results of supramalleolar osteotomy for varus-type ankle osteoarthritis. J Bone Joint Surg Am. 2022;104(5):412-420.
4. Wang JW, Chen TH, Hsu CC, et al. Medial opening-wedge supramalleolar osteotomy for varus ankle osteoarthritis. Orthopedics. 2021;44(3):e345-e351.
5. Park JH, Lee KT, Kim KC, et al. Dome-shaped supramalleolar osteotomy for complex ankle deformities. Foot Ankle Surg. 2020;26(6):645-650.
6. Choi YR, Lee KT, Kim KC, et al. Comparison of lateral closing wedge and medial opening wedge supramalleolar osteotomy for varus ankle osteoarthritis. Knee Surg Sports Traumatol Arthrosc. 2019;27(4):1234-1240.
7. Hintermann B, Valderrabano V, Boss A, et al. Supramalleolar osteotomy for the treatment of varus ankle osteoarthritis. Foot Ankle Int. 2004;25(7):462-471.
8. Valderrabano V, Hintermann B, Nigg BM, et al. Gait analysis after supramalleolar osteotomy for varus ankle osteoarthritis. Clin Biomech. 2006;21(2):168-175.
9. Kim MS, Lee KT, Park YU, et al. Survivorship of supramalleolar osteotomy for ankle osteoarthritis: a minimum 10-year follow-up. Am J Sports Med. 2023;51(2):432-439.
10. Zhang L, Liu Y, Wang X, et al. Outcomes of supramalleolar osteotomy for ankle malalignment: a systematic review and meta-analysis of 1,200 patients. J Orthop Surg Res. 2023;18:145.
11. Gougoulias NE, Khanna A, Maffulli N. Supramalleolar osteotomies for the treatment of ankle osteoarthritis. Br Med Bull. 2009;92:107-123.
12. Barg A, Pagenstert G, Hefti AF, et al. Realignment surgery for valgus ankle osteoarthritis. Arch Orthop Trauma Surg. 2007;127(10):853-860.
13. Lee KT, Kim KC, Park YU, et al. Fibular osteotomy in supramalleolar osteotomy: is it necessary? Foot Ankle Int. 2018;39(5):567-573.
14. van Hoeve S, van der Velden J, van Dalen KC, et al. Patient-specific instrumentation in supramalleolar osteotomy: a randomized controlled trial. Arch Orthop Trauma Surg. 2021;141(8):1345-1352.
15. Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957;16(4):494-502.
16. Woon CY, Poon SC, Tay SC, et al. Supramalleolar osteotomy for ankle osteoarthritis: a minimum 5-year follow-up. Foot Ankle Int. 2016;37(10):1091-1097.
17. Lee KB, Bai LB, Park JH, et al. Comparison of clinical and radiological outcomes between opening and closing wedge supramalleolar osteotomy. Knee Surg Relat Res. 2017;29(3):183-189.
18. Choi HJ, Lee KT, Kim KC, et al. The effect of fibular osteotomy on the outcome of supramalleolar osteotomy. Foot Ankle Surg. 2019;25(4):456-461.
19. Labib SA, Amendola A. Realignment osteotomies about the ankle. J Am Acad Orthop Surg. 2002;10(2):85-93.
20. van der Walt A, Myerson MS. Realignment osteotomies of the ankle. Foot Ankle Clin. 2011;16(4):643-658.