This lady presented three years following a left total hip arthroplasty, with hip dislocation which was reduced in the operating theatre. She had also suffered two prior dislocations. One month later she had persistent left hip discomfort and instability. An x-ray and CT were performed in preparation for revision surgery.
Our patient's initial x-ray showed dislocation of the left hip (Figure 1). One month after closed reduction of the dislocation a follow-up x-ray was performed (Figure 2). The femoral component of the left prosthesis was noted to be excessively supero-laterally located within the acetabular cup, with no other abnormality noted. The patient had persistent left hip discomfort and given the recurrent dislocations a CT was ordered by the orthopaedic surgeons as part of a work-up for revision total hip arthroplasty surgery (Figures 3, 4 and 5). An unexpected circular hypo-dense lesion was incidentally seen within the the soft tissues of the posterior left thigh, although the patient had not been experiencing any symptoms in this exact region. This represented the liner component of the total hip arthroplasty which had become dislodged during dislocation reduction one month prior. In retrospect it could also be visualised on the follow-up x-ray (Figure 2).
Dislocation is one of the most common serious complications after total hip replacement. It has an annual rate of up to 10% and is a major concern for both patients and surgeons [1, 2]. It is also the most common indication for revision surgery [3].
In total hip arthroplasty, the liner fits into the acetabular component and allows the femoral head component to glide easier and more naturally in the socket. It is usually composed of plastic or ceramic. Common liner-related complications include wear leading to loosening and ceramic fracture [4]. Dissociation of the liner component is rarely seen [5]. Migration of the liner into the soft tissues around the hip following dislocation has not been described however.
In this case the liner cannot be seen within the soft tissues on the initial dislocation x-ray suggesting that migration occurred during reduction of the dislocation. The presence of the liner within the soft tissues of the thigh was not initially noted on the follow-up x-ray and only identified incidentally on CT as part of work-up for revision surgery. Given the patients history the appearances are readily suggestive of the diagnosis despite its extreme rarity. Clinically it was not clear whether the abnormal position of the liner was causing symptoms distinct from the ongoing hip discomfort and instability.
Liner migration such as this requires surgical management. This patient underwent revision left total hip arthroplasty and the liner was removed from an encapsulated pocket in the posterior thigh.
Take Home Message: Migration of the liner component of total hip arthroplasty into the soft tissues around the hip can occur during reduction following dislocation. It is readily visualised on x-ray and CT and requires surgical removal and revision hip surgery.
Total hip arthroplasty liner soft tissue migration following dislocation reduction
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From the provided left hip joint X-ray, the femoral stem and acetabular shell of the prosthesis appear generally stable. However, the liner, which should be located inside the acetabular component, is not visible in its proper position. Instead, a dense shadow can be seen in the soft tissues of the left thigh (posterior soft tissue), corresponding to the liner. CT scans further confirm a circular, dense prosthetic component in the peri-hip soft tissue, consistent with the migrated liner.
Overall, there is no obvious loosening of the acetabular component itself, but the liner is clearly separated from the acetabular component and appears as a mass in the left thigh soft tissue, indicating it has dislocated or “migrated” from its original location. Considering the patient’s history of two previous hip dislocations, it is likely that the liner displacement is related to prior surgical reduction or repeated dislocations.
Based on radiological findings and the patient’s history, the potential diagnoses include:
Taking into account the patient’s advanced age of 78 years, history of left hip arthroplasty (with repeated dislocations), and clear radiological evidence revealing ectopic placement of the liner in the left thigh soft tissue, the most likely final diagnosis is:
Left hip prosthetic liner dislocation and migration into the thigh soft tissue.
This is an extremely rare situation. The patient’s history of repeated dislocations suggests significant joint instability, and surgical intervention is needed to remove the dislocated liner and perform revision surgery on the joint.
Considering this patient’s advanced age, history of multiple hip dislocations, and previous revision surgeries, rehabilitation should be individualized and increased progressively.
Throughout the rehabilitation process, the exercise prescription should follow the FITT-VP principle:
• Frequency: 3–5 times per week.
• Intensity: Initiate with low to moderate intensity (heart rate no more than 60–70% of maximum) and gradually increase.
• Time: Start with 10–15 minutes per session, gradually extending to 30 minutes or more.
• Type: Progress from passive and active joint mobility exercises to aerobic and resistance training, focusing on low-impact activities.
• Progression: Adjust intensity and duration according to individual recovery and functional status.
• Volume and Pattern: Flexibly modify while maintaining safety as the top priority.
Additionally, when designing the exercise regimen, the patient’s bone health, cardiopulmonary function, and risk of redislocation must be carefully considered to ensure all activities are performed safely.
Disclaimer: The above analysis and recommendations are for reference only and do not substitute for an in-person consultation or professional physician’s advice. Specific treatment plans should be determined by qualified orthopedic surgeons and rehabilitation professionals based on the patient’s individual condition.
Total hip arthroplasty liner soft tissue migration following dislocation reduction
