A 63-year-old woman presented with one-and-a-half-year history of avascular necrosis of both femoral heads under bisphosphonate treatment and complaint of left-hip atraumatic pain. Pain has been present for several months and caused the patient to refrain from work. The patient also had six-year history of seronegative arthritis.
The patient underwent plain radiography (Fig. 1) that was reported to show unchanged avascular necrosis of both femoral heads, and subsequently magnetic resonance imaging (MRI) was performed to clarify the symptoms. MRI performed two weeks later (Figs. 2-3) showed a near-vertical fracture line extending through the left femoral neck and proximal shaft, and little bone marrow oedema suggesting that the fracture was not acute. The femoral cortex was interrupted at multiple sites, including lateral neck and proximal shaft. Subchondral collapse in avascular necrosis of the left femoral head was also seen (stage 3 according to Ficat and Arlet classification of avascular hip necrosis) and likely contributed to the patient’s symptoms. No subchondral collapse of the right femoral head was present (stage 2 according to Ficat and Arlet classification of avascular hip necrosis).
Background. Bisphosphonates reduce bone turnover by inhibiting osteoclastic activity and can be used to prevent subchondral collapse in early avascular necrosis of the hip.
Clinical perspective. Prolonged bisphosphonate use may however result in the accumulation of bone microdamage and lead to complications, such as an atypical femoral fracture. According to the American Society for Bone and Mineral Research, this is defined as a transverse fracture due to low-energy trauma at the subtrochanteric area and diaphysis [1]. Rarely, a vertical fracture of the femoral neck has also been observed in patients taking long-term bisphosphonate without any associated trauma [2, 3]. In our case, a near-vertical fracture of the femoral neck and proximal shaft occurred within one-year-and-a-half of bisphosphonate therapy.
Imaging perspective. Imaging is required for diagnosis. Bisphosphonate-related vertically oriented fracture line of the femoral neck starts on the lateral cortex, as it is the tension side, and then progresses distally [2, 3]. In our case fracture was complete because proximal shaft cortex was also interrupted.
Outcome. Bisphosphonate-related femoral neck fractures show high delayed union and non-union rates when treated with internal fixation, because bisphosphonates inhibit bone healing [3]. Arthroplasty may thus be worth considering, particularly in our case due to the coexisting subchondral collapse of the left femoral head. In our patient, bisphosphonate treatment was discontinued, crutches were introduced to aid gait and the patient was then referred to the orthopaedic surgeon.
Take home message. Physicians should be aware of this condition, when managing patients with early-stage avascular necrosis of the hip under conservative treatment with bisphosphonates and onset of atraumatic pain.
Written patient consent for this case was waived by the Editorial Board. Patient data may have been modified to ensure patient anonymity.
Insufficiency vertical fracture of the proximal femur after bisphosphonate treatment
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1. From the anteroposterior (AP) pelvic X-ray, structural changes can be observed in both femoral heads. The left femoral head shows signs of subchondral fracture or collapse, suggesting progression of avascular necrosis (AVN).
2. In the left femoral neck region, a nearly longitudinal hairline is visible, extending to the lateral cortex of the proximal femoral shaft, consistent with a potential "atypical" fracture presentation.
3. On the coronal MRI, there is a low/mixed signal area in the left femoral head, corresponding to avascular necrosis; meanwhile, a linear high or low signal change can be seen in the femoral neck, indicating a longitudinal fracture line. In some areas, the signal is interrupted, corresponding to a fully formed fracture.
4. Local subchondral collapse of the left femoral head is noted; no obvious abnormal swelling or mass is seen in the surrounding soft tissues. The right hip joint shows fewer signal changes, but there is a known history of avascular necrosis of the femoral head.
Among these differentials, the most consistent with current imaging and case history is: avascular necrosis with a superimposed bisphosphonate-related atypical fracture (particularly the longitudinal fracture in the left femoral neck).
Considering the patient's age (63 years), symptoms (persistent left hip pain without a clear trauma), medical history (bilateral femoral head avascular necrosis, prolonged bisphosphonate therapy, and a 6-year history of seronegative arthritis), and imaging findings (a nearly longitudinal fracture line in the femoral neck along with collapse of the left femoral head), the most likely diagnosis is:
"Atypical left femoral neck fracture related to bisphosphonates on the basis of femoral head avascular necrosis."
1. Medication and Other Conservative Treatments:
• Evaluate the necessity of pausing or replacing bisphosphonate therapy to avoid further risk of fracture and impaired bone healing capacity.
• Supplement with appropriate amounts of vitamin D and calcium if needed, to improve bone health.
• For pain or inflammation, use NSAIDs or appropriate analgesics under medical supervision.
2. Surgical Intervention:
• For “atypical” femoral neck fractures with femoral head collapse, total hip arthroplasty may be considered.
• If collapse is not evident or the patient is not suitable for arthroplasty, assess the feasibility of internal fixation, though delayed or non-union is a concern.
3. Rehabilitation and Exercise Prescription:
(1) Early Phase (Preoperative or Non-Surgical Conservative Stage)
• Use crutches or a walker to reduce weight-bearing on the affected limb; consider partial or restricted weight-bearing based on pain level and fracture stability.
• Engage in low-intensity, short-duration joint mobility exercises, such as performing active or passive hip flexion and extension in bed to reduce joint stiffness.
(2) Intermediate Phase (Initial Postoperative Rehabilitation or After Fracture Stabilization)
• Gradually increase the weight-bearing. If a hip replacement was performed, follow the surgeon’s protocol, progressively conducting exercises for hip range of motion and muscle strengthening.
• Perform gentle isometric and isotonic exercises around the hip joint, focusing on the iliopsoas and quadriceps to enhance support and stability.
(3) Late Phase (Functional Consolidation and Return to Daily Activities)
• Once pain subsides and fracture healing is sufficiently stable, gradually increase exercise intensity, such as slow walking in water or stationary cycling, which imposes less impact on the joint.
• Follow the FITT-VP principles (frequency, intensity, time, type, progression, and individualization): 3-5 times per week, low-to-moderate intensity, 20-30 minutes per session, and increase according to tolerance and progress.
• Monitor hip pain and function to avoid overexertion and secondary injury.
Note: The above rehabilitation plan must be individualized based on the patient’s cardiopulmonary condition and bone quality. If severe pain or discomfort occurs during any exercise, discontinue and seek medical advice promptly.
Disclaimer: This report is for medical reference only and does not replace in-person consultation or professional medical advice. If you have any doubts or experience changes in your condition, please consult a specialist in a timely manner.
Insufficiency vertical fracture of the proximal femur after bisphosphonate treatment
