Introduction
The fibula is a primarily non-weight-bearing bone-estimated weight distribution of 6.4%-of the lower leg, extending from the inferolateral aspect of the tibial plateau distally to make the lateral malleolus of the ankle. The most proximal portion, known as the fibular head, is the site of attachment for the biceps femoris tendon and lateral collateral ligament. The common peroneal nerve bifurcates into the deep and superficial branches just inferior to the fibular head and neck. The peroneal muscles originate from the mid and proximal aspects of the lateral border of the fibula and provide some soft tissue protection in regard to direct trauma. The tibiofibular syndesmosis, a fibrous attachment between the fibula and tibia, provides stability for the lateral malleolus and with forces of external rotation on the ankle (Fields, 2019; Takebe, Nakagawa, Minami, Kanazawa, & Hirohata, 1984; Wheeless, 2012).
Fibula fractures are most commonly the result of a traumatic incident, like a fall or impact/collision during sports. Most common are fractures of the mid-diaphysis and proximal third of the fibula. Independent of trauma, risk factors include low bone density, advanced age, being female, and cigarette smoking. Fibular fractures may also occur due to repetitive loading activities, such as running, but these are more commonly referred to as stress fractures or injuries (Bhadra, Roberts & Giannoudis, 2012; Fields, 2019; Sanders, Tieszer, & Corbett, 2012; Wheeless, 2012).
Fracture healing is divided into three stages: inflammation, repair, and remodeling. During the inflammation stage a hematoma forms and an array of macrophages, neutrophils, and platelets releases cytokines. Fibroblasts and mesenchymal cells migrate to the area forming granulation tissue about the fracture site. There is associated proliferation of osteoblasts and fibroblasts. During repair, primary callus forms and enchondral ossification converts soft callus to hard callus via expression of Type II followed by Type I collagen. The amount of callus is directly related to the extent of immobilization. The remodeling phase begins during repair and continues on for months after clinical healing. This involves a complex set of pathways that ultimately organizes osteoblastic and osteoclastic activity to form new bone. Several patient factors, including smoking/nicotine use, poor nutritional status, and comorbid medical conditions such as diabetes mellitus, vascular disease or HIV, can negatively impact bone healing (Aiyer, 2018).
Case Presentation
A 64-year-old woman presented for evaluation of left lateral lower leg pain associated with a fall that occurred 5 weeks prior. She had slipped on an icy sidewalk, notes lunging to her side and, in an attempt to keep her balance, forcefully planting the left foot. She then fell over onto her left side. She endorsed painful weight bearing thereafter, with swelling about the lower leg noted later that evening. She presented to a local emergency department (ED) the following day where radiographs were obtained, read as "normal," and she was diagnosed with a knee strain (see Figure 1). The ED staff fitted her for a knee brace and crutches, with instructions to rest, ice, and take nonsteroidal anti-inflammatories for her symptoms. She returned home the following week, noting continued lower leg pain, and so scheduled an appointment with her primary care provider. Primary care obtained radiographs of the left tibia and fibula and these were also read as being "normal" (see Figure 2). She was instructed on continued conservative management and to follow up with orthopaedics. She had discontinued use of crutches, noting them to be too cumbersome.
Upon presentation she was an alert, oriented, affect appropriate female in no apparent distress. She ambulated with an antalgic gait, without use of an assistive device. The leg was without gross deformity, swelling, or discoloration. There was tenderness about the proximal fibula with a negative squeeze. Lower leg compartments were soft and compressible. Knee and ankle range of motion were grossly equal, with mild patellofemoral crepitus noted bilaterally. The patient reported posterior knee, as well as posterolateral lower leg, pain with end-range knee flexion. Her knee and ankle were stable with ligamentous testing. Strength was grossly equal and sensation was intact to light touch distally. She was unable to perform a single-leg stance given pain.
Radiographs obtained at the time of orthopaedic evaluation were evident for a healing, nondisplaced proximal fibula fracture (see Figure 3). Note the central resorption and early callus formation. Alignment is overall maintained. A retrospective review of the outside ED images revealed incongruence of the posterior cortex and buckling of the lateral cortex of the proximal fibula (refer to Figure 1) and early signs of healing in the subsequent tibia/fibula series (refer to Figure 2).
Management
Given the patient's continued pain at the time of diagnosis, she was instructed to resume use of crutches and knee brace. Instruction on protected weight bearing and activity limitations, allowing pain to be her guide, was reinforced. We also discussed gentle range-of-motion exercises to prevent stiffness. She continued with anti-inflammatories, Tylenol, and icing as needed. Two weeks later, the patient contacted this provider noting significant improvement in symptoms and requesting referral to physical therapy. She was able to wean off crutches over the following week and returned for evaluation in the following weeks (Fields, 2019; Wheeless, 2012).
At that time she was nontender but did still note discomfort with more than 20-30 minutes of walking. Follow-up radiographs, as well as her clinical presentation, were consistent with continued healing (see Figure 4) and she was instructed to continue with physical therapy for gait training and modalities.
The patient returned 5 weeks later, approximately 4 months from date of injury, noting resolution of symptoms. She had taken a vacation the week previous and had done several hours of site seeing/"exploring" each day. She noted no issues with this and was very pleased to report the progress. Imaging obtained at that time showed continued evidence of healing and maintenance of osseous alignment (see Figure 5).
Discussion
Although isolated fibula fractures are relatively rare, it should be considered in the list of differentials for any patient presenting with lateral lower leg pain, especially in the setting of a direct trauma or reported repetitive impact activities. Plain radiographs are typically sufficient for diagnosis although subtle, nondisplaced fractures may be difficult to appreciate immediately after an acute injury. The advanced practice orthopaedic provider should take care in examining patients, with a high level of suspicion and low threshold for obtaining follow-up imaging, in those with focal tenderness about the lateral lower leg. Findings of concomitant tibial involvement, or those presenting with knee or ankle instability, should be worked up accordingly and referred to an orthopaedic surgeon for definitive treatment. The advanced practice orthopaedic provider can offer reassurance that the majority of isolated fibula fractures will heal appropriately with time and conservative measures (Bhadra et al., 2012; Fields, 2019; Kothari, Tikoo, Saini, & Dalvie, 2015; Sanders et al., 2012; Wheeless, 2012).
References