Early Weight-Bearing Following Ankle Fracture ORIF: Pertinent Pearls And Pitfalls
Ankle fractures are common orthopedic injuries, accounting for approximately 20 percent of lower extremity trauma.1 Of these fractures, greater than 50 percent are relatively predictable in that the etiology is a supination-external rotation-type mechanism.2 When these injuries are unstable (ie deltoid ligament rupture, medial malleolar avulsion fracture, syndesmotic involvement, posterior malleolar involvement), open reduction and internal fixation (ORIF) is an option to achieve realignment of the ankle mortise back to its original anatomic state.1 Proper preoperative planning and surgical technique are essential considerations for optimal osseous healing and return to normal function; however, determining postoperative protocols such as immobilization duration and weight-bearing status are also important. A contemporary question when considering these injuries is if there is compromise of osseous bridging when initiating early weight-bearing. Or, does it simply aid in an earlier return to normal activities without compromised healing? In this submission, we aim to discuss the normal biomechanics and kinetics of the ankle joint and attempt to critically evaluate the medical literature comparing traditional versus early weight-bearing protocols following ankle fracture ORIF.
Ankle Joint Biomechanics And Pathomechanics: What You Should Know
When considering bipedal motion, it is clearly important to understand the role of the ankle joint in sagittal plane motion at the junction of the foot and the leg.3 The ankle joint includes the tibia and fibula’s distal articular surfaces and the talus’s trochlear surface. The talus is broader anteriorly than posteriorly and is depressed centrally, which corresponds to the articular surface of the distal tibia.3 The malleoli reside medial and laterally to the talar body. The lateral malleolus position is more posterior and distal than the medial malleolus, which corresponds to the ankle joint axis. These periarticular surfaces gain support from the medial and lateral collateral ligaments, which stabilize and limit available sagittal plane range of motion.3
The oblique nature of the ankle joint also allows some transverse and frontal plane motions, again corresponding to the angular deviation of the malleoli. This axis will deviate plantar-medially with plantarflexion and plantar-laterally with dorsiflexion. Again, the axis parallels the position of the malleoli with approximately 10 to 30 degrees of dorsiflexion.3 When the foot is in open-chain kinetics, the primary movement will occur in the sagittal plane with associated abduction with dorsiflexion and adduction with plantarflexion. The stability of the joint surfaces strongly depends on ligamentous integrity. If there is excessive laxity or injury, there will be a shift in the ankle joint’s axis of rotation and movement.3
Skeletal tissue remodeling is resilient in acute or chronic injury settings and might alter the architecture of the ankle in response to certain mechanical forces.4
With a specific type of injury, for example, a rotational ankle fracture, the loading forces on the bone produce hydrostatic pressure gradients that cause interstitial fluid to form outside the lacunae of bone.4-6 This, in turn, will allow extra-cellular signals such as nuclear factor-κ ϐ ligand and osteoprotegerin to accumulate and start the reparative phase of osseous healing. However, different signals and cellular activity take place based on the site and size of the osseous injury. Small-or moderate-size strain will favor the release of osteoblasts, whereas larger strain will cause an increase in fibroblastic activity and may lead to a fibrous union.6,7 Understanding the gap strain placed upon the fracture site can allow the surgeon to more accurately evaluate fixation construct options that might also affect postoperative protocols.
Understanding How Fixation Technique Can Influence Stability Postoperatively
Fixation constructs have evolved throughout the years, allowing for more intuitive application and better outcomes in terms of osseous bridging and return to activity.8 Before surgical intervention, one should consider several factors, including age, sex, co-morbidities, fracture pattern, and bone quality. As mentioned previously, understanding the normal biomechanics of the ankle joint can guide surgeons towards more appropriate fixation of ankle fractures.8 Bone undergoes both static and dynamic forces such as torque, axial loading, and bending. These physiologic loads translate to bone from muscle forces as well as weight-bearing status. One can realign a typical spiral oblique fracture caused by a supination-external rotational force using a lag compression screw and a neutralization plate.9 With a lag compression screw, the type of compression is called static interfragmentary compression, and allows for stability but does not provide much strength. To allow for early mobilization after internal fixation with an interfragmentary screw, the use of neutralization plates will help protect the compression site of the fracture from torsional, bending, and shearing forces. If there is a concern for vascular compromise or osteoporotic bone, one can use a locking plate to avoid screw loosening from poor bone quality, preserve the periosteum, and provide a stiffer construct to improve rigidity of the screw-plate construct.8,9
If a fracture is in the metaphyseal or epiphyseal bone and there is comminution, lag screw fixation alone will not withstand the deforming shear and bending forces. In these circumstances, a locking buttress plate will prevent axial deformity and support the construct. With buttress plating, the surgeon must insert the screw fixation so there will be no shift in the plate position when put under axial load. Common buttress plating techniques can occur for tibial plateau fractures or pilon fractures.9 Like the fibula, the medial malleolus can undergo similar axial loading forces, shearing, torsional, or bending forces. It is important to recognize different types of ankle fracture patterns for identification of proper fixation techniques such as 4.0 mm cannulated screws or hook plates.9
Randall and colleagues performed a biomechanical cadaveric study to compare dual non-locked plating to locked plating systems for comminuted fibular fractures.9 In their study, fixation of all right fibula specimens were with a four-hole lateral locking plate and four, 2.7mm locking screws distally and three, 3.5mm cortical screws proximally. For the left fibula specimens, fixation consisted of seven-hole one-third tubular plates with three, 3.5mm cortical screws proximally and two, 4.0mm cancellous screws distally and a seven-hole, 2.4mm mini-fragment adoption plate with two, 2.4mm cortical screws proximally and three, 2.4mm cortical screws distally.10 The authors applied external rotational torque and measured torsional stiffness, torque, and load to failure. Results indicated no significant difference in stiffness at 0.25 to 0.5 nm and 0.5 to one nm between the two groups, and there was no statistical difference in torque at 10 degrees of external rotation.10 Based on the authors’ conclusions, dual plating is a viable fixation option in comminuted distal fibular fractures for which locking plate fixation is not applicable for comminuted distal fibular fractures.10
Taking it a step further in identifying biomechanical failures with fixation and possibly early weight-bearing, Tan and colleagues similarly performed a cadaveric study to evaluate the biomechanics of early weight-bearing after surgical fixation of unstable ankle fractures. Secondarily, these authors wanted to evaluate the amount of displacement with early loading and correlate displacement with bone mineral density.11 Researchers divided 24 fresh frozen cadavers into three groups: Group 1, bimalleolar ankle fractures (n=6); Group 2, trimalleolar ankle fractures without posterior malleolar fixation (n=9); and Group 3, trimalleolar ankle fractures with fixated posterior malleolar fractures. Fracture fixation was with a 3.5mm interfragmentary screw and a neutralization locking compression fibular plate with three, proximal 3.5mm non-locking screws and four, distal 2.7mm locking screws. Posterior malleolar fracture fixation was with one, 4.0 mm partially-threaded cannulated screw. Medially malleolar fracture fixation was with with two, 4.0 mm partially-threaded cannulated screws. Specimen exposure to axial compression loading simulated the load of adult weight-bearing. With each simulated ankle fracture group (bimalleolar, trimalleolar with and without posterior malleolar fixation), there was no significant fracture displacement and no displacement or failure of hardware failure.11 In terms of secondary outcomes, there was no correlation between fracture displacement and bone mineral density. Overall, the authors supported early weight-bearing protocols after fixation of unstable ankle fractures.11
How Might Surgeons Determine Timing Of Weight-Bearing After ORIF?
The traditional postoperative course following ankle fracture ORIF is non-weight-bearing cast immobilization. This is generally due to a fear of construct failure prior to osseous healing.11 However, early weight-bearing might expedite an earlier return to work, subsequently minimizing the economic impact of fractures and lessening altered gait mechanics.11
There is a substantial amount of literature that supports early weight-bearing after ankle fracture ORIF. An important article by Ahl and colleagues utilized a prospective, randomized controlled trial to compare patients undergoing isolated fibular ankle ORIF with pins, cerclage wires, and staples.12 The control group remained non-weight-bearing in a below-knee cast until postoperative week four, and the experimental group began weight-bearing on postop day one in a below-knee cast. The authors concluded that there was no significant difference in loss of reduction based on radiographic findings at 12 and 24 weeks, and no difference in swelling and range of motion (ROM) among both groups with minimal fixation constructs such as cerclage wire and staples.12 Similarly, a year later, Ahl and colleagues evaluated and compared patients with bimalleolar and trimalleolar ankle fracture ORIF with immediate weight-bearing on postoperative day one in a below-knee cast versus non-weight-bearing for four weeks.13 Again, the authors found no difference in loss of reduction between the two groups and no difference concerning swelling or range of motion with similar constructs of cerclage wire, pins, or staples.13 On a larger scale, a Cochrane meta-analysis of three studies compared early and late weight-bearing after ankle fracture fixation.14,15 Among these studies, there was no significant difference in functional scores, range of motion, or radiographic outcomes after weight-bearing.14-16
Traditional non-weight-bearing protocols post ankle fracture ORIF last approximately six weeks, and the rationale is to prevent fracture displacement, hardware failure, or an overall increase in complications.17-19 However, many studies to date challenge that protocol and demonstrate that early weight-bearing could restore early range of motion, prevent osteoporosis, and avoid skin atrophy.17-19 Honigmann and colleagues utilized a vacuum-stabilized orthosis and prescribed full weight-bearing after two weeks. They compared this with a functional regimen of partial weight-bearing of 15kg for six weeks after lateral malleolar ORIF using a one-third tubular plate with or without a plate-independent compression screw construct.20 The early weight-bearing orthosis group demonstrated improved functional outcomes and reduced swelling with statistically significant improvement in health outcome scores and no significant difference in complication rates compared to the partial weight-bearing group.20,21
Schubert and colleagues recently evaluated patients undergoing unimalleolar, bimalleolar, or trimalleolar ankle fracture fixation with interfragmentary screw and plate fixation with weight-bearing at two weeks versus six weeks.22 All patients initially used a below-knee posterior splint and remained non-weight-bearing for the first two postoperative weeks. After suture removal, patients began use of a controlled ankle motion walking boot and underwent random selection to either weight-bearing or non-weight-bearing groups. Patients who were non-weight-bearing were to stay off their affected side for six weeks and allowed range outside the boot three times a day. Those allocated to the early weight-bearing group could weight-bear as tolerated and perform daily active and passive range of motion. According to their results, the early weight-bearing group did not demonstrate a significant improvement in functional outcome scores at six weeks; however, early weight-bearing did statistically improve the overall health status of patients clinically at six weeks.22
A recent multi-center randomized control study by Smeeing and colleagues assessed unprotected non-weight-bearing, protected weight-bearing, and unprotected weight-bearing as tolerated with patients undergoing Lauge Hansen supination external rotation (SER) ankle fractures.23,24 The authors defined unprotected non-weight-bearing as mobilization with crutches and performance of active ankle exercises without casting or braces. These patients had a pressure dressing placed for the first 24 hours postoperatively and remained non-weight-bearing for six weeks. They defined protected weight-bearing as weight-bearing as tolerated. Initially, patients were placed in a posterior splint for 10 days, then transitioned to a weight-bearing below-knee cast for six weeks. Finally, unprotected weight-bearing included a pressure dressing for the first 24 hours postoperatively, after which patients were allowed to weight-bear as tolerated without casting. All these patients started mobilization specific to their postoperative protocol. The authors also included fixation constructs as follows: two screw fixation; screw fixation and neutralization plate; and dorsolateral buttress plate for the fibular fractures, with fixation technique determined by the surgeon’s preference. The authors concluded that unprotected weight-bearing and early mobilization improved short-term functional outcomes and early return to work.23,24
Concluding Thoughts
Although many of the reviewed publications are likely at risk for selection bias due to the retrospective nature of the data collection, it is reasonable to conclude that many contemporary publications support early weight-bearing after ankle fracture ORIF. It might be challenging to accept changes to historical protocols, but the evidence behind the benefits of early mobilization for these patients makes a compelling argument in support of early weight-bearing.
Dr. Mateen is a fourth-year resident at the Temple University Hospital Podiatric Surgical Residency Program in Philadelphia.
Dr. Levi is a third-year resident at the Temple University Hospital Podiatric Surgical Residency Program in Philadelphia.
Dr. Kwaadu is a Clinical Associate Professor in the Department of Surgery at Temple University School of Podiatric Medicine in Philadelphia.
Dr. Meyr is a Clinical Professor in the Department of Surgery at Temple University School of Podiatric Medicine in Philadelphia.
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