Overview
Every malunion presents a unique set of bone deformities, described by abnormalities of length, angulation, rotation and translation. Describing the location, magnitude and direction of the deformity completes its characterization. Accurate assessment lets surgery follow an effective plan to correct the deformity. (Rockwood)
Clinical Assessment
Take the history from the date and mechanism of the original fracture and all later operative and nonoperative treatment. Record previous wounds and bone infection, with prior culture reports. Note preinjury medical problems, disabilities and associated injuries, current pain, functional limits and medications. (Rockwood)
Examine skin and soft tissue for previous incisions, active drainage or sinuses.
Stress the malunion manually to exclude motion and to assess pain. A solidly healed malunion should not hurt under manual stress. If it does, consider that it may actually be a nonunion. (Rockwood)
Do a neurovascular examination and assess active and passive motion of the joints above and below the malunion. Reduced motion in an adjacent joint changes both the plan and the expected functional result. (Rockwood)
Compensatory joint deformity. In periarticular malunion, an adjacent joint can develop a fixed compensatory deformity. Correcting the malunion without addressing it leaves a malaligned joint with a straight bone, and a disabled limb. The limb may look aligned while radiographs show the joint deformity. If the joint cannot be placed parallel to the malunion deformity (for example the subtalar joint cannot be turned into valgus in a tibial valgus malunion), the joint deformity is fixed and needs correction. (Rockwood)
Radiographic Assessment
Original fracture films show the type and severity of the first injury. Serial films show implant status (loose, broken, undersized) and when implants were placed or removed. Assess how the deformity developed (gradual or sudden). (Rockwood)
Obtain AP and lateral radiographs including the joints above and below to assess the axes of the bone. For lower-limb deformities, obtain bilateral standing, long-leg (51-inch) AP and lateral alignment films. Flexion/extension laterals help define the arc of motion of adjacent joints. (Rockwood)
Use the films to document limb alignment, joint orientation, anatomic axes, mechanical axes and the center of rotation of angulation (CORA), and compare with normative values. Manual measurement and computer-assisted measurement are equally accurate. (Rockwood)
Limb alignment
Measure the mechanical axis of the whole limb in the frontal plane on a weight-bearing AP long-leg film with the feet pointing forward (neutral rotation).
Mechanical axis deviation (MAD) is the distance from the knee joint center to the line joining the hip and ankle joint centers. The hip center is the center of the femoral head, the knee center is midway between the tibial spine tips and the apex of the femoral intercondylar notch, and the ankle center is the center of the tibial plafond.
Normally the mechanical axis passes 1 to 15 mm medial to the knee center. More than 15 mm medial is varus malalignment, and any lateral deviation is valgus malalignment. (Rockwood)
Axes and joint orientation
Anatomic axis: a line through the center of the diaphysis along the bone (each angulated segment has its own axis).
Mechanical axis of a long bone: a line through the joint centers proximal and distal. For the femur, the proximal half of the mechanical axis normally lies outside the bone.
Joint orientation lines are drawn in the frontal and sagittal planes. Joint orientation angles relate them to the anatomic or mechanical axis.
Normal lower-limb values (Rockwood Table 31-1):
Femur, frontal: mechanical lateral proximal femoral angle (mLPFA) 90 degrees (range 85–95); neck–shaft angle 130 (124–136); mechanical lateral distal femoral angle (mLDFA) 88 (85–90); anatomic lateral distal femoral angle (aLDFA) 81 (79–83); anatomic medial proximal femoral angle (aMPFA) 84 (80–89).
Tibia, frontal: medial proximal tibial angle (MPTA) 87 (85–90); lateral distal tibial angle (LDTA) 89 (88–92).
Tibia, sagittal: anterior distal tibial angle (ADTA) 80 (78–82).
Abnormal limb alignment is not necessarily due to knee malorientation. (Rockwood)
CORA (center of rotation of angulation)
The CORA is where the proximal and distal axes of a deformed bone intersect. The angle between them is the angular deformity in that plane. Use either anatomic or mechanical axes, but do not mix them.
If a joint orientation is abnormal, either a second CORA exists in that plane (multiapical deformity) or there is a translation deformity.
The bisector line passes through the CORA and halves the angle between the proximal and distal axes. Angular correction on the bisector gives full correction without creating translation, and every point on it can be considered a CORA for planning. (Rockwood)
Describing each deformity type
Length: measured joint center to joint center on radiographs with a marker to correct magnification, compared with the normal limb. Shortening comes from bone loss or overlap. Overdistraction at fixation can cause overlengthening. Lower limb: up to 2 cm is treated with a shoe lift, tolerance of a 2 to 4 cm lift is poor, and most patients with more than 4 cm of shortening benefit from restoring bone length. In the upper limb, up to 3–4 cm of shortening is usually well tolerated. (Rockwood)
Angulation: magnitude and apex direction. Diaphyseal angulation usually relates to MAD. Oblique-plane deformity can be calculated from AP and lateral measurements by trigonometry (oblique magnitude = arctan of the square root of tan²(frontal) + tan²(sagittal)) or by the graphic (Pythagorean) method, which is accurate within about 4 degrees unless both planes exceed 45 degrees. If CORAs are at different levels on AP and lateral films, there is translation in addition to angulation. (Rockwood)
Rotation: measured by clinical examination, axial CT, or trigonometric or graphic calculation. Clinical measurement is usually accurate enough. For tibial malrotation, compare the foot axis (second toe to the center of the calcaneus) to the tibial anatomic axis. For the femur, the patient lies prone with the knee at 90 degrees and the femoral condyles parallel to the table. Internal and external rotation of the tibia are measured and compared with the other side (adjusting for any tibial angulation). (Rockwood)
Translation: described by the direction of the distal segment relative to the proximal segment and measured as the horizontal distance between the two anatomic axes at the level of the proximal end of the distal segment. (Rockwood)
Treatment Planning (Rockwood)
Characterize the deformity by type (length, angulation, rotation, translation or combined), apex direction, plane of orientation, magnitude and level of the CORA.
Evaluate the soft tissues. Preoperative planning may require assessing overlying flaps and skin grafts. Scar, tethered neurovascular bundles and infection can change the plan. If neurovascular structures lie on the concave side of an angular deformity, acute correction can cause traction injury, so gradual correction is preferred to let nerves and vessels adapt.
Decide which deformities actually need correction. Small translation deformities or sagittal-plane angulation may not affect function and can be left. Then plan the order and method of correction.
Osteotomy Principles (Rockwood)
An osteotomy divides the deformed bone to realign the anatomic and mechanical axes. The relationship between the osteotomy level, the CORA and the correction axis determines the result:
Osteotomy, CORA and correction axis at the same location: realignment by angulation only, with no translation.
CORA and correction axis together, but osteotomy proximal or distal: realignment by angulation plus translation.
CORA different from the correction axis and the osteotomy: angular correction aligns the axes in parallel but produces excess translation, an iatrogenic translation deformity.
Osteotomy types by cut: transverse or wedge, dome (actually cylindrical) and clamshell. By type: open, neutral or closed.
Wedge osteotomy. If the CORA and correction axis are on the convex cortex, correction is an open wedge and lengthens the bone (the concave cortex distracts and opens a wedge). If both are at mid-bone it is a neutral wedge with no effect on length (the concave cortex distracts, the convex cortex compresses, and a wedge is removed from the convex side). If both are on the concave cortex it is a closed wedge, which shortens the bone (the convex cortex is compressed and a wedge of full diameter removed). The same principles apply when the osteotomy is proximal or distal to the shared CORA location, but then correction occurs through angulation plus translation.
Dome osteotomy. The osteotomy never passes through the CORA/correction axis, so translation always occurs. Ideally the CORA and correction axis lie reciprocally to the osteotomy so that the angulation and the forced translation realign the bone axis. If not, a translation deformity results. Open, neutral and closed dome osteotomies lengthen, preserve or shorten the bone. Because dome surfaces rarely block movement of one segment over another, bone usually does not need resection unless it overhangs substantially. A dome osteotomy is often needed for juxta-articular deformities, where the CORA is too close to the joint for a wedge osteotomy.
Clamshell osteotomy. A simplified technique for diaphyseal malunions: a longitudinal cut along the deformed segment plus transverse cuts at its proximal and distal ends. An intramedullary nail then aligns the proximal and distal diaphyseal segments along the anatomic axis, correcting angulation and translation in the coronal and sagittal planes, while the osteotomized pieces heal to each other and to the main segments by secondary bone healing. Set rotation and length before locking the nail, using the opposite limb as a template. It reduces planning complexity for single-plane osteotomies, and can be used for acute fractures near an existing diaphyseal malunion.
Choice of osteotomy depends on type, size and direction of deformity, proximity to a joint, location and effect on soft tissues, and the chosen fixation. In some cases a small iatrogenic deformity is acceptable if it will not affect function, rather than using an unfamiliar fixation method. (Rockwood)
Treatment by Deformity Type (Rockwood)
Length. Acute or gradual correction. Acute lengthening and shortening are limited by soft tissues, open wounds and neurovascular structures. Acute lengthening distracts the bone ends to the proper length, fills the gap with bone graft (autogenous cancellous or cortical, vascularized autograft, bulk or strut allograft, mesh cage-graft constructs, or synostosis techniques) and stabilizes. Acute shortening resects bone and compresses the ends. In the forearm and leg, the intact bone needs a partial excision (for example the fibula) to allow shortening of the tibia. Gradual correction typically uses a tensioned-wire (Ilizarov) external fixator, but also monolateral fixators or a motorized lengthening nail. It uses a corticotomy (usually metaphyseal) and distraction of 1 mm/day in four 0.25-mm increments, with bone forming by distraction osteogenesis. It can correct associated angular, translation or rotational deformity at the same time.
Angulation. Osteotomy, realignment and fixation, acutely or gradually. Gradual correction suits neurovascular structures or poor soft tissues on the concave side. Diaphyseal angulation is ideal for a wedge osteotomy at the CORA, and juxta-articular angulation often needs a dome osteotomy with the osteotomy proximal or distal to the CORA/correction axis.
Rotation. Osteotomy, rotational realignment and stabilization.
Translation. Three options: a single transverse osteotomy for pure translation; a single oblique osteotomy at the level of the deformity to correct alignment and gain length; or two wedge osteotomies of equal magnitude in opposite directions at the two CORA levels, treating translation as two equal and opposite angulations.
Combined deformities. Define and characterize each deformity independently, decide which need correction, and plan the order and method. Often one osteotomy can correct two deformities: for example angulation plus translation through one osteotomy at the apex of the angulation, or angulation plus rotation through an oblique axis. For a combined angulation–rotation deformity, rotate the distal segment about an oblique axis. The axis angle in radians is arctan(rotation/angulation), and the osteotomy plane inclination in degrees is 90 minus (axis angle in radians × 57.3). For example, 20 degrees of angulation and 30 degrees of rotation give a 56-degree axis inclination and a 34-degree osteotomy plane. The osteotomy passes through the CORA of the angulation, and rotation in the osteotomy plane around this axis realigns the bone (a rotation of 36 degrees in the source example). Rotation not about a CORA causes secondary translation, which can be corrected afterward.
Postoperative Care and Complications
Postoperative management depends on the fixation chosen (intramedullary nail, plate, external fixator). The source chapter text used for this guide does not specify a single rehabilitation protocol.
Recognized problems include iatrogenic translation from a mismatch of osteotomy, CORA and correction axis, traction injury to neurovascular structures with acute correction of a deformity that tents them, uncorrected compensatory joint deformity, and nonunion. (Rockwood)
References
Chapter 31, principles of malunion treatment. In: Tornetta P III, Ricci WM, Ostrum RF, McKee MD, Ollivere BJ, de Ridder VA, eds. Rockwood and Green's Fractures in Adults. 10th ed. Wolters Kluwer; 2024 (Turkish edition: Erişkin Kırıkları).