What Is a Medial Buttress in Bone Mechanics and Surgery?

A medial buttress is a load-bearing structure, either natural bone or a surgically placed plate, positioned along the inner (medial) side of a bone to resist the forces that would otherwise cause it to collapse or shift. In orthopedic surgery the term most often refers to a small plate screwed onto the medial cortex of a fractured bone to prevent the broken fragment from shortening or angulating under body weight. But the concept reaches beyond hardware: the medial buttress principle shows up in the natural architecture of the skull, in veterinary diagnostics for torn ligaments in dogs, and even in fossil analysis of early human ancestors. Understanding where and why this inner support matters explains a surprisingly wide slice of how bones work under load.

How the Medial Side of a Bone Carries Load

Bones are not solid rods. They have thick outer walls of compact bone and an interior lattice of spongy bone arranged along the lines of greatest stress. In the proximal femur, for instance, computational models show that both standing on two legs and standing on one leg produce compressive stresses that travel through distinct internal pathways. Areas of greater structural density focus those stresses through an arch-like internal architecture, channeling force from the hip joint down through the femoral neck and into the shaft.¹ The medial cortex, the inner wall of the bone closest to the body’s midline, sits right under the peak of that compressive load. When a fracture disrupts this cortex, the entire mechanical chain breaks down and the bone fragments can telescope into each other or drift into a poor alignment that won’t heal.

This is why surgeons pay so much attention to restoring medial support. A fracture that leaves a gap on the medial side is inherently unstable because body weight keeps pushing the fragments together in a direction nothing is resisting. The goal of a medial buttress, whether achieved through careful fracture reduction or by bolting on a small plate, is to rebuild that inner wall so the bone can carry load again while it heals.

Medial Buttress Plates in Femoral Neck Fractures

Femoral neck fractures, the breaks that occur just below the ball of the hip joint, are notoriously difficult to fix. The fracture line often runs nearly vertical, which means the shearing forces trying to slide the head fragment off the neck are enormous. Standard fixation with cannulated screws alone can fail, especially when the fracture is steep or when bone along the inner cortex (the calcar) is missing or crushed.

Adding a small medial buttress plate to supplement those screws changes the biomechanics substantially. A finite element analysis comparing a medial anatomical buttress plate to other fixation strategies found that the plate produced a more stable construct, with better stress distribution and less displacement of the bone fragments along the axis of loading.² A separate biomechanical study comparing cannulated screws alone, cannulated screws plus a medial buttress plate, and intramedullary nails for vertical femoral neck fractures with calcar defects confirmed that the screws-plus-plate combination provided additional stability beyond what screws alone could offer.³

A 2025 systematic review pooling data across multiple studies reported that when cannulated screws were combined with a medial buttress plate, the failure rate was about 15%, compared with roughly 27% when a dynamic hip screw was paired with the same plate, though that difference did not reach statistical significance.⁴ This suggests that the choice of primary implant still matters and that the buttress plate works best as a supplement to fixation that already has a good mechanical match with the fracture pattern.

In cases where the fracture is old, meaning weeks have passed since the injury, surgeons sometimes combine the medial buttress plate with cannulated screws and bone graft harvested from the patient’s pelvis. This approach addresses three problems at once: the plate restores medial wall support, the screws compress the fracture, and the graft fills in bone that has been resorbed during the delay.⁵

Medial Cortical Support in Intertrochanteric Fractures

Intertrochanteric fractures occur slightly lower than femoral neck fractures, through the region between the greater and lesser trochanters. In unstable patterns, the posteromedial cortex is often broken into multiple fragments. How well the surgeon restores that medial cortex during the operation turns out to be one of the strongest predictors of outcome.

The concept here is “positive medial cortical support,” which means the shaft fragment is positioned so its medial cortex slightly overlaps or props up the head-neck fragment from below, rather than sitting flush or leaving a gap. This nonanatomic alignment allows the head-neck fragment to slide a small, controlled amount along the implant until it contacts the shaft and locks into a stable configuration. That secondary stability provides a favorable environment for healing.⁶

A recent study measured functional recovery in patients with unstable intertrochanteric fractures and found that those who achieved positive medial cortical reduction had markedly better walking ability scores at every follow-up point compared with patients who had neutral or negative reduction. By twelve weeks, the positive-reduction group averaged about 19 out of a possible score, versus lower scores in the other groups.⁷ The clinical message is clear: a surgeon who gets the medial cortex right during the initial operation gives the patient a measurably better chance at getting back on their feet quickly.

Screw Placement and Plate Failure

A medial buttress plate is a small piece of hardware, often only a few centimeters long, bent to conform to the curve of the bone. It sits directly in the high-stress zone, so the details of how it is attached matter. One of the practical debates involves whether screws through the plate should engage only the near (medial) cortex or pass all the way through both cortices of the bone.

A scanning electron microscopy study compared plates fixed with unicortical screws (grabbing only the near cortex) to those fixed with bicortical screws (passing through both cortices) in a model of steep femoral neck fractures. Plates with bicortical screws showed significantly more microdamage, including plastic deformation, microcracks, and in some specimens complete fractures, particularly at the bent midsection of the plate. Unicortical plates, by contrast, showed only mild surface irregularities without structural failure.⁸

The likely explanation is that bicortical screws create a more rigid connection between the plate and the bone, which sounds like an advantage but actually concentrates stress at the plate’s weakest point, the bend. A unicortical grip allows a small amount of micromotion that distributes stress more evenly. This is one of those areas where the intuition that “stronger attachment equals better results” can lead surgeons astray. The research suggests that for medial buttress plates on the femoral neck, unicortical fixation may actually protect the plate from fatigue failure.

The Proximal Humerus and the Medial Column

The same buttress logic applies to the upper arm. Proximal humeral fractures, the breaks near the shoulder, often involve loss of the medial calcar, a thick ridge of bone on the inner side of the humerus just below the head. When that calcar is missing or crushed, a standard locking plate on the outer (lateral) side of the bone struggles to maintain alignment. The humeral head tends to collapse inward, a deformity called varus collapse, which wrecks shoulder function.

Patients with intact medial calcar support after locking plate fixation had significantly less impaction of the fracture and higher functional scores on the affected side compared with patients who had medial calcar deficiency.⁹ When the calcar cannot be restored by bone-to-bone reduction, surgeons can add a supplemental medial buttress plate. A study of proximal humeral fractures with an unstable medial column found that adding a medial buttress plate after lateral locking plate fixation effectively prevented varus collapse and implant failure.¹⁰

Another approach uses an intramedullary calcar support plate, a small plate inserted inside the bone canal, combined with the lateral locking plate. In elderly patients with complex three- and four-part proximal humerus fractures, this combination maintained fracture reduction and prevented the humeral head from collapsing or tilting, with satisfactory early clinical results.¹¹ The theme across all these techniques is the same: a lateral plate alone is fighting gravity and muscle pull without a foundation, and the medial buttress provides that foundation.

Tibial Plateau Fractures

The tibial plateau, the flat top of the shinbone that forms the bottom half of the knee joint, is another site where medial buttress plating plays a critical role. Fractures of the posteromedial plateau are especially tricky because the fragment sits behind the knee, making it hard to reach surgically, and the fracture line is often vertical, meaning the fragment wants to slide downward under body weight.

A cadaver study comparing a medial buttress plate to a lateral locked plate for vertically oriented medial tibial plateau fractures found that the medial buttress plate provided significantly greater stability under static loading and trended toward better stability under repeated loading cycles.¹² The reason is geometric: a plate placed directly behind or beside the fragment that wants to displace can push back against it, whereas a plate on the opposite side of the bone can only pull through screws, which is a weaker form of control.

Arthroscopy-assisted techniques have improved surgeons’ ability to reduce these fractures precisely. In a series of 25 patients with posteromedial tibial plateau fractures treated with arthroscopy-guided reduction and buttress plate fixation, all fractures healed and 92% achieved good or excellent clinical and radiologic outcomes.¹³ The arthroscope lets the surgeon look directly at the joint surface during the operation to confirm that the cartilage is smooth and the fracture edges are lined up, without needing to open the entire knee.

Medial Buttresses in the Face

The concept extends well beyond the limbs. The human facial skeleton is built to absorb and distribute the forces of chewing, and it does this through a system of thickened bony columns sometimes called buttresses. A finite element study of the mid-facial skeleton under biting loads identified five vertical and two horizontal buttress pathways through which occlusal forces travel from the teeth up into the skull base.¹⁴ The nasomaxillary buttress, running along the side of the nose, is one of the medial vertical struts traditionally described in surgical textbooks as crucial for facial reconstruction after trauma.

However, this classical buttress model has come under scrutiny. A computational biomechanical study found that during maximal bite force, the lateral maxilla carried the primary vertical load, with much smaller involvement of the nasomaxillary buttress than textbooks suggest.¹⁵ And a review of bone strain studies and finite element models went further, arguing that the available data on bone material properties do not actually support the existence of discrete pillars and buttresses in the way they are traditionally taught, and suggesting that the model be replaced with more nuanced computational approaches.¹⁶

This matters for surgeons reconstructing facial fractures. If the traditional buttress map overstates the importance of certain struts while understating others, then plating strategies based on that map may not be optimally placed. The field is moving toward patient-specific computational models that predict actual load paths rather than relying on a one-size-fits-all anatomical diagram.

The Medial Buttress in Veterinary Medicine

In veterinary orthopedics, “medial buttress” refers to something quite different: a firm, fibrous thickening on the inner side of the stifle (knee) joint in dogs. When the cranial cruciate ligament tears, either partially or completely, the resulting instability triggers chronic inflammation and scar tissue formation. Over time, a palpable lump of fibrosis develops on the medial aspect of the joint. This medial buttress is considered virtually diagnostic for cruciate ligament rupture in dogs, particularly in cases where swelling from fluid in the joint is hard to feel because the tear happened long enough ago that the acute effusion has subsided.¹⁷

Veterinarians check for this finding during a physical examination by running their fingers along the inner side of the dog’s knee. A positive medial buttress, combined with instability on the cranial drawer test, points strongly toward a cruciate tear even without advanced imaging. Cruciate disease is one of the most common orthopedic problems in dogs, particularly in larger breeds, so this clinical sign comes up frequently in general practice. It is worth noting that this use of the term “medial buttress” has nothing to do with plates or hardware; it describes a pathological tissue response, a case where the body tries to stabilize a joint on its own by building a fibrous wall where the ligament used to do the job.

An Evolutionary Trace in Fossil Bone

Deep inside the proximal femur sits a plate of dense bone called the calcar femorale, located just behind the lesser trochanter. This internal buttress reinforces the femoral neck against the bending and compressive loads of walking upright. Its presence has drawn the attention of paleoanthropologists because it may carry information about when our ancestors adopted habitual bipedal locomotion.

CT scans of a six-million-year-old femoral fragment from the early hominin Orrorin tugenensis revealed a calcar femorale with strong anatomical similarity to that of modern humans. A statistical classification test grouped this ancient specimen with Homo sapiens rather than with non-bipedal primates, supporting the interpretation that Orrorin was an early biped.¹⁸

The picture has gotten more complicated since that initial analysis. A broader study examining the calcar femorale across a wider range of fossil and living hominids found that the structure was absent in one Paranthropus robustus specimen and variably developed in other fossils. The authors concluded that the calcar femorale cannot be treated as a reliable diagnostic marker for habitual bipedal walking and called for more research into what exactly drives its development.¹⁹ The internal medial buttress of the femur may reflect bipedalism, but it may also respond to other loading patterns, individual variation, or body size differences. Using any single anatomical feature to diagnose locomotor behavior millions of years after the fact is risky, and the calcar femorale debate illustrates that nicely.

Why Surgeons Obsess Over the Medial Side

Across the hip, shoulder, knee, and face, the recurring theme is that the medial cortex or medial column bears a disproportionate share of compressive load. Gravity pulls the body’s mass downward through structures that are offset from the center of the bones supporting them. The femoral head sits at an angle to the shaft. The humeral head overhangs the shaft medially. The tibial plateau receives asymmetric loads from the knee. In every case, the medial wall is the one under compression, and compression is what bone handles best, but only if the wall is intact.

When that wall breaks, no amount of hardware on the opposite side fully compensates. A lateral plate can resist bending forces, but it cannot replace the medial column’s role as a compressive strut. That is why the trend in fracture surgery over the past two decades has been toward dual-plating constructs and toward meticulous surgical reduction of the medial cortex, even when it means accepting a slightly nonanatomic alignment. Getting the medial buttress right, whether with bone or metal, is often the difference between a fracture that heals uneventfully and one that collapses into a deformity requiring a second operation.