The Use of a Cuboid Notch in Foot Orthotics

Foot orthotics, also known as orthoses, are custom-made or prefabricated inserts placed inside shoes to support, align, or improve the function of the feet. They play a crucial role in managing various musculoskeletal conditions, from simple foot pain to complex biomechanical imbalances that affect the entire lower body. Among the myriad modifications available in orthotic design, the cuboid notch stands out as a specialized feature tailored to address issues related to the lateral midfoot. This essay explores the use of the cuboid notch in foot orthotics, delving into its definition, anatomical relevance, functions, benefits, applications in treating specific conditions, fabrication process, and supporting insights from podiatric practice. By examining this modification, we can appreciate how subtle design elements in orthotics contribute to overall foot health and mobility.

To understand the cuboid notch, it is essential to first grasp the anatomy of the foot. The human foot comprises 26 bones, divided into the hindfoot, midfoot, and forefoot. The cuboid bone, located in the midfoot on the lateral (outer) side, is a cube-shaped tarsal bone that articulates with the calcaneus (heel bone) posteriorly, the fourth and fifth metatarsals anteriorly, and the lateral cuneiform medially. It serves as a pivotal point in the lateral column of the foot, facilitating stability during weight-bearing activities and acting as a pulley for the peroneus longus tendon, which wraps around its plantar surface to insert into the first metatarsal base. This tendon helps in everting the foot and plantarflexing the first ray, crucial for propulsion during gait. However, due to repetitive stress, trauma, or biomechanical faults like excessive pronation (inward rolling) or supination (outward rolling), the cuboid can become subluxated—partially dislocated—leading to pain, instability, and altered mechanics. Conditions such as cuboid syndrome arise from this misalignment, characterized by sharp lateral foot pain, swelling, and difficulty walking, often exacerbated by activities involving inversion or plantarflexion.

The cuboid notch is a targeted modification in foot orthotics designed to interact with this bone. It is typically a subtle indentation or contoured space on the lateral plantar surface of the orthotic, positioned just proximal to the styloid process of the fifth metatarsal. This depression accommodates the prominent plantar-lateral aspect of the cuboid, preventing it from being compressed or forced into a plantar-flexed position. In fabrication, it involves removing approximately 3 to 5 mm of plaster from the plantar lateral aspect of the positive foot model, enhancing the lateral inclination angle of the calcaneus to provide an upward force that resists subluxation and stabilizes the calcaneocuboid joint. Interestingly, the term "cuboid notch" can encompass both intrinsic and extrinsic variations. The intrinsic notch is built directly into the orthotic shell, raising its height under the cuboid via cast or scan prescription, while the extrinsic version uses an added pad, such as a rectangular Myolite or poron padding on the superior lateral surface. This pad, often wedge-shaped and varying in thickness from as thin as a grain of rice to a stack of three nickels, sits beneath the distal lateral frame to offload pressure. Both approaches aim to support the lateral column, but the choice depends on the patient's needs—intrinsic for seamless integration, extrinsic for adjustable cushioning.

The primary functions of the cuboid notch revolve around stabilization, offloading, and motion facilitation. By creating a contoured space or supportive elevation, it prevents the cuboid from "dropping" plantarly, thus eliminating pressure points that could worsen subluxation. This stabilization restores the integrity of the cuboid pulley mechanism, reducing strain on the peroneus longus tendon and surrounding ligaments for more efficient function. Additionally, it offloads excessive forces from the lateral midfoot, distributing load more evenly across the metatarsal heads and minimizing compensatory movements like excessive supination or pronation. In terms of motion, the notch provides a solid foundation for the lateral column, promoting normal gait mechanics and improving first metatarsophalangeal joint (MPJ) rotation during propulsion. For instance, in orthotics for high-impact sports, it enhances lateral stability by creating a pronatory moment or lateral orthopedic reactive force (ORF), which counters instability.

These functions translate into significant benefits for patients. The notch reduces tendinous irritation and inflammation, particularly in the peroneus longus, alleviating pain and swelling in the outer midfoot. It also contributes to a "three-point" correction system in pronated feet, combining with medial arch support to guide the foot into neutral alignment, thereby preventing midfoot collapse and excessive strain on the plantar fascia. Athletes and active individuals benefit from improved shock absorption and gait efficiency, reducing the risk of recurrent injuries. Moreover, by addressing biomechanical imbalances, it can mitigate upstream issues like knee pain or lower back discomfort stemming from foot dysfunction. Custom orthotics incorporating this feature offer superior comfort compared to over-the-counter options, as they redistribute body weight evenly and limit excess motion that exacerbates subluxation.

One of the most common applications of the cuboid notch is in treating cuboid syndrome, a condition often underdiagnosed but prevalent among runners, dancers, and those with flat feet or ankle sprains. In this syndrome, the cuboid subluxates due to trauma or repetitive stress, causing sharp pain on weight-bearing. Orthotics with a cuboid notch or pad help by providing cushioning and support to the bone, realigning it and preventing further displacement. After manual manipulation to reduce the subluxation, a pad applied plantarly resists plantar flexion, while low-dye strapping complements the orthotic to pull the foot medially against the peroneus longus force. The notch is also effective for lateral ankle instability, peroneal tendinopathy, and plantar fasciitis, where it prevents "unfolding" of the midfoot and reduces inflammation. For oversupinators, it promotes better mechanics to decrease syndrome risk, while in pronators, it corrects excessive motion to maintain proper calcaneocuboid alignment.

Fabrication of orthotics with a cuboid notch requires precision and clinical expertise. It begins with a thorough assessment: palpating the foot for cuboid prominence or tenderness, evaluating gait biomechanics, and using casts or scans to create a positive model. The notch is then incorporated by modifying the model—removing plaster for the depression or adding material for a pad—ensuring the surrounding orthotic is semi-rigid for support yet edged with softer materials to avoid irritation. Placement is critical: on the outer midfoot, directly below the cuboid, to avoid creating new pressure points. Practitioners often combine it with other modifications, like arch supports or heel postings, for comprehensive correction. It's not universal; suitability depends on individual foot type, activity level, and pathology, often used post-manipulation for maintenance.

Expert insights underscore the effectiveness of this modification. Podiatrists note that the cuboid notch can be particularly beneficial in managing midtarsal joint stress, enhancing overall orthotic performance when paired with motion-enhancing techniques. While specific large-scale studies are limited, clinical experience from sources like orthotic labs and podiatry networks highlights its role in pain relief and recurrence prevention. For visual clarity, consider the design in custom orthotics:

The cuboid notch represents a sophisticated yet understated advancement in foot orthotic design, bridging anatomy and biomechanics to offer targeted relief. By stabilizing the cuboid, offloading stress, and optimizing motion, it addresses a range of conditions from cuboid syndrome to broader instabilities, enhancing patient outcomes without invasive interventions. As podiatric practices evolve, such modifications underscore the importance of personalized orthotics in preventive and rehabilitative care. With ongoing refinements, the cuboid notch continues to exemplify how small architectural tweaks can yield profound improvements in foot function and quality of life.

Craig Payne is a University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger and a dad.