A 47-year-old male patient complains of bilateral lower leg pain at his first presentation and subtle pretibial swelling after occasional running. He had a total thyroidectomy in 1996. His vitamin D3 level is in the lower normal range (60nmol/l). Six years later, he returns with similar pain in both femora.
Conventional radiographs of both lower legs in 2007 show adjacent lucencies in the anterior cortex (Fig.1a+b) of both tibiae with minor pretibial soft tissue swelling on the right. Follow-up image of the right tibiae in 2013 shows a small residual horizontal radiolucent line in the anterior cortex (Fig.2). Bone scintigraphy from 2007 (Fig.3) presents symmetrical longitudinal linear signal intensities along the anterior tibial cortices with focal hotspots. Less pronounced longitudinal cortical tracer uptake is visible in both femora. Follow-up bone scintigraphy in 2013, obtained because of recurrent pain - now in the femora - demonstrates subtle residual longitudinal linear signal along both tibiae and now two symmetrical focal hotspots in the femoral midshafts and proximal femora. CT of the femoral midshafts (Fig.4a) obtained in 2013 demonstrates bilateral intracortical low density lesions. High-resolution CT shows an area of gray cortex (Fig.4b) with an adjacent irregular small horizontal fracture line (Fig.4b-d) without signs of periosteal reaction.
Although stress fractures may arise in many different bones of the body, the lower extremities are more prone to insufficiency due to higher tensile forces during upright movement. Stress fractures can be subdivided into fatigue (mechanical overload of normal bone) or insufficiency (normal loading of weakened bone) fractures [1]. In our patient the low vitamin D level may have contributed to osseous insufficiency due to hypomineralisation of bone. Stress fractures of the tibiae are typically seen in runners, ballet dancers and military recruits, more frequently in untrained individuals [1-6].
The term ‘shin splints’ used in this context derives from the clinical presentation of patients with pain around the shin and summarizes a variety of tibial pain syndromes including the ‘medial tibial stress syndrome’(MTSS) that is generally associated with periosteal soft tissue changes in the antero- or postero-medial circumference of the tibiae. Many authors [5, 6] believe that MTSS is a precursor stage of stress fractures and the underlying pathophysiology affecting the muscle-bone unit is a continuous process rather than a single event although the location of pain in shin splints and MTSS and radiologically documented stress fractures vary in the literature [1-6]. This discrepancy may also be due to the imaging modality employed in each case and insufficient resolution in order to depict fine fracture lines in many cases only visible with high resolution CT.
Prevalent sites for radiologically proven stress fractures are anterior midshaft and distal tibia and medial or lateral femoral midshaft. Transverse fractures are more common than vertical ones.
Positive bone scintigraphy (linear pattern in MTTS precede focal hotspots in stress fractures) has a sensitivity of almost 100% in the depiction of stress fractures thus presenting the method of choice [3, 4]. Scintigraphy and MR signal changes precede radiographic changes by weeks. Mulligan and others [2, 5, 7] describe the “gray cortex sign” around stress fracture sites (Fig.4) which most likely represent areas of increased intracortical remodelling as demonstrated by SPECT images of transverse femoral fractures sites (Fig.5a+b). Especially when this gray cortex sign presents without obvious transverse fracture lines, the radiologist may be faced with a diagnostic challenge. Therapeutic options include either limitation of external forces, e.g. training rest or modify internal material properties by strengthening the muscle-bone unit by physical therapy or correction of calcium-phosphate-metabolism (Vit.D substitution in our case). Radiographic proof of true fracture lines will result in adaption of treatment duration.
Tibio-femoral stress fractures (syn. shin splints)
1. From the provided lower limb X-rays (tibia, femur) and subsequent bone scan and CT images, the following observations can be made:
• Mild cortical density changes in the mid-lower tibia and the femoral shaft, with some areas showing the “gray cortex sign.”
• On the CT cross-sectional images, there are limited lucent areas beneath the cortex of the tibia/femur, but no obvious transverse fracture line is necessarily seen.
• The bone scan indicates areas of increased radiotracer uptake in these locations, suggesting possible active bone remodeling or a stress response.
2. Clinically, the patient experiences bilateral calf or thigh pain following running or weight-bearing, which is consistent with the stress-related changes seen in the tibia and femur on imaging.
3. A history of total thyroidectomy and low vitamin D levels suggests a degree of suboptimal bone mineralization or endocrine-metabolic factors that can make bones more susceptible to stress injuries or decreased bone density.
Combining the patient’s recurrent pain after running, low vitamin D levels, the “gray cortex sign” on imaging, and increased uptake on the bone scan, the most likely diagnosis is bilateral tibial and femoral shaft stress fractures (stress reaction or incomplete fracture).
Further definitive diagnosis should include clinical physical examination, follow-up imaging (such as repeat X-ray, MRI, or high-resolution CT), and assessment of bone metabolic markers (calcium, phosphorus, parathyroid hormone, etc.). When a clear fracture line appears at a later stage, the diagnosis may be confirmed.
1. Conservative Treatment:
• Weight-bearing Management: Reduce or suspend high-impact activities (e.g., running, jumping), switching to low-impact exercises (e.g., swimming, cycling) to maintain cardiorespiratory fitness and lower limb strength. Gradually return to full activity once symptoms subside.
• Correction of Bone Metabolism: According to test results, supplement vitamin D and calcium as needed; evaluate parathyroid function if necessary to prevent impaired bone remodeling.
• Physical Therapy and Strength Training: Physical therapy can help promote local blood circulation and reduce inflammation; strength training should focus on calf and thigh muscles to improve the biomechanical balance of the bone-muscle unit, reducing stress concentration.
2. Surgical Treatment:
• If a clear, unstable stress fracture occurs and conservative measures fail or the fracture line progresses over time, surgical intervention (e.g., internal fixation) may be considered. However, this is not typically the first choice.
3. Rehabilitation / Exercise Prescription (FITT-VP Principle):
• Frequency: In the early stages, 2-3 sessions of low-impact aerobic exercise (e.g., elliptical, swimming) per week are recommended. As symptoms improve, gradually increase to 3-4 sessions per week.
• Intensity: Maintain moderate to low intensity (subjective effort at about 60-70% of maximum heart rate), strictly avoiding any significant aggravation of pain. In later rehabilitation, introduce light strength exercises to build muscle stability.
• Time: Begin with 20-30 minutes per session, gradually extending to 30-40 minutes. Follow a stepwise approach, reducing activity if pain or discomfort appears.
• Type: Emphasize low-impact, continuous aerobic activities, supplemented by resistance band or light-load strength training for the lower limb muscles.
• Progression: If there is no pain or only mild discomfort, increase training volume or intensity by 10-20% every 2-3 weeks. If symptoms recur, revert to the previous stage.
4. Precautions:
• If bone quality is compromised due to previous thyroid treatments or vitamin D deficiency, implement a cautious and progressive approach when designing the exercise program, avoiding any high-impact or explosive movements.
• Regularly monitor bone metabolism and muscle strength. If pain worsens or new symptoms appear, promptly return for further evaluation.
Disclaimer:
This report is based on a reference analysis of existing imaging and medical history information and cannot replace in-person consultations or the opinions of professional physicians. Clinical diagnosis and treatment should be combined with the patient’s actual condition, with comprehensive judgment and management carried out by a licensed physician.
Tibio-femoral stress fractures (syn. shin splints)
