Posterior dislocations of the hip are orthopedic emergencies often resulting from high-energy trauma. When associated with acetabular fractures and neglected for a prolonged period, they become surgically demanding due to soft-tissue contractures, cartilage damage, and joint incongruity ^[1,2]. Total hip arthroplasty (THA) is a well-established solution in chronic or irreducible dislocations, especially when osteonecrosis or secondary arthritis has developed ^[3]. However, the challenge intensifies in patients with prior surgeries that alter biomechanics, such as patellectomy. The patella plays a crucial role in knee extensor efficiency, and its absence may affect gait, limb alignment, and rehabilitation potential after THA ^[4]. In cases with acetabular bone loss, reconstruction cages provide structural support, restoring load-bearing capacity and joint congruency [5-7]. We present a rare case of neglected posterior dislocation with acetabular fracture in a patient with prior patellectomy, managed with THA and acetabular cage application.

A 42-year-old male presented to our trauma unit 2 months following a fall from height, complaining of persistent right hip pain, inability to bear weight, and limb shortening. The patient initially received conservative treatment at a peripheral center without imaging.

Past medical history

Ten years prior, the patient underwent right-sided patellectomy following a comminuted open patellar fracture. No other comorbidities were present.

Examination

Physical examination revealed a shortening of 4 cm, an internally rotated right lower limb, and reduced hip range of motion. Quadriceps strength was diminished due to previous patellectomy, though the knee joint remained stable.

Radiology

X-rays and computed tomography (CT) scan confirmed a neglected posterior dislocation of the right hip with a comminuted fracture of the acetabulum involving the posterior wall and column (Fig. 1-7). The femoral head showed early degenerative changes.

Surgical management

A posterior approach was used. Intraoperative findings included severe acetabular comminution and segmental bone loss. A reinforcement cage with a cemented acetabular cup was implanted. An uncemented femoral stem was inserted with attention to restoring limb length and offset. Stability was confirmed intraoperatively. Post-operative X-ray was done (Fig. 8).

Post-operative care

The patient followed a structured rehabilitation protocol with gradual weight-bearing. At 6 months, he was ambulatory without support, pain-free, and had satisfactory hip range of motion.

Neglected posterior dislocations with acetabular fractures are rare due to the disabling nature of the injury, but can occur in under-resourced settings or when initial treatment is inadequate ^[2,8]. In chronic cases, the femoral head may develop osteonecrosis or cartilage damage, making arthroplasty a preferred solution ^[3]. The use of acetabular cages is well supported in revision settings and complex primary THA, particularly when there is segmental or cavitary bone loss ^[5,6,9]. These constructs allow restoration of the center of rotation, limb length, and long-term implant stability. The presence of prior patellectomy introduces unique biomechanical considerations. The loss of the patella diminishes the quadriceps lever arm, increasing rehabilitation challenges and potentially influencing lower limb alignment ^[4,10]. Despite these concerns, this patient achieved excellent outcomes, demonstrating the feasibility of THA even in the presence of altered biomechanics. This report describes a single patient and, as such, findings cannot be generalized. Anatomical and biomechanical variations may yield different outcomes in similar clinical scenarios. The 6-month follow-up period provides only preliminary insight into long-term durability, implant survival, and patient function. Longer-term evaluation is needed. No objective gait or biomechanical analysis was conducted to assess compensatory mechanisms post-patellectomy, which may influence hip loading patterns. Comparative analysis with other treatment options – like conservative therapy, delayed fixation, or custom 3D-printed implants – was not performed. This limits the assessment of relative efficacy. The imaging presented did not include advanced modalities such as CT-based 3D reconstruction for pre-operative planning or post-operative implant integration analysis. Standardized functional scoring tools, such as the Harris Hip Score or Western Ontario and McMaster Universities Osteoarthritis Index, were not utilized to objectively measure clinical outcomes. While previous patellectomy was acknowledged, its specific long-term effects on hip joint biomechanics and compensatory gait adaptations were not comprehensively explored. (Fig. 9).

This case illustrates that THA with cage reconstruction is a reliable option for managing neglected posterior hip dislocation with acetabular fracture, even in the presence of biomechanical compromise due to prior patellectomy. Early diagnosis, individualized planning, and careful surgical execution are critical to achieving favorable outcomes in such complex cases.

Acetabular cage-assisted THA offers a viable solution in complex hip trauma with previous biomechanical alterations, such as patellectomy, provided comprehensive planning and follow-up are implemented.