Neglected hip dislocations often occur in children and are rarely reported in adults. This study showed effective correction of limb length discrepancy and significant functional improvement with external fixation-assisted reduction in thirteen adult patients. Though skeletal traction is important in joint reduction, the acetabulum becomes filled with fibrous tissue in neglected dislocations would make reduction difficult by simple traction. Skin traction usually carries a weight under 5 kg. Halo-femoral and tibial tubercle traction can carry more weight but it often ends with unsatisfactory results in patients with neglected hip dislocation [9, 17]. Prolonged dislocation may cause severe joint contracture so it is difficult to achieve satisfactory reduction by regular traction. Furthermore, heavy traction may lead to neurovascular complications.
Common complications of traumatic hip dislocation include infection, sciatic nerve palsy, AVN, heterotopic ossification, and post-traumatic arthritis . Previous studies have reported that the incidence of arthritis was 16–30%, and 8.1–10% for AVN in the mid-to-long-term follow-up [1, 19]. The blood supply to femoral head is often damaged by traumatic dislocation, especially the medial femoral circumflex artery. Vascular compromise leads to intravascular coagulation and ischemic necrosis, resulting in chondral failure and accelerated joint degeneration . A high incidence of osteonecrosis has been reported from 10 to 25% in hip dislocations . Furthermore, the severity of the injury and time to reduction are associated with increased risks of osteonecrosis . The rate of osteonecrosis is only 10% in adults after simple dislocation, but reaches 70% if the dislocation is accompanied by severe bony destruction such as fracture of the femoral head and acetabulum . Hougaard and Thomsen reported that the rate of osteonecrosis of the femoral head can be reduced from 58 to 4.8% if hip reduction is performed within the first 6 h following injury . Others have concluded a trend for decreased osteonecrosis of the femoral head when hip reduction was performed within 12 h . In our patients, AVN occurred in 2 patients (15%), and osteoarthritis occurred in 1 patient (7.7%). All 3 patients suffered acetabular fractures with an average duration from injury to surgery of 6.3 months (range, 4 to 8 months). Patient 6 (Table 1) showed AVN 10 months after the surgery, and the Merle d’Aubigne score was improved from 4 to 12. Patient 7 (Table 1) showed AVN 12 months after surgery, and the Merle d’Aubigne score was improved from 5 to 13. Patient 11 (Table 1) showed osteoarthritis at the last follow-up (14 months), and the score was improved from 4 to 11. Though complications occurred, patients demonstrated significant functional improvement. Previous studies have also reported that complications continue to occur within 5 years [7, 24], though our study only reports a short-term follow-up result within 18 months. As the incidence of secondary complications may increase with time , an accurate complication rate should be recalculated for long-term follow-up.
THR has been recommended for hip dislocations with a duration of more than 3 months , but usually provided limited correction of limb length discrepancy within 6 cm [11, 12] and muscle release may be needed for improved correction . It may provide limited efficacy for patients in this case series which all suffered limb inequality of more than 5 cm. Considering all patients were under 50 years and no signs of necrosis or arthritis occurred when on admission, we decided to perform open reduction and fixation after traction. Follow-up results showed significant pain relief and function improvement. The satisfactory rate of clinical outcome was 53.8% (excellent and good results). Limb length discrepancy was effectively corrected, and no patient was left with > 2 cm of inequality, thereby laying the foundation for possible THR in the future. AVN and arthritis occurred in three patients. Though they showed unsatisfactory outcomes (two poor and one fair), none of them received further treatment at the last follow-up. A further study evaluating the long-term clinical outcomes of external fixation with delayed open reduction against total hip replacement is required.
From our experiences, external fixation was effective for pre-reduction in patients suffering from neglected hip dislocations with limb length discrepancy, but still several contraindications are noteworthy. First, this treatment option should not be used in patients with heterotopic ossification, which most commonly occurs in the hip joint, and the incidence after traumatic dislocation was 32 to 37% [27, 28]. Traction would be resisted by ectopic bone. As the fixation technique requires stable anchors, it is unfit for patients with an unstable pelvic ring or femur. Furthermore, patients with osteoporosis should not be considered because osteoporotic bone may fail under power of traction.
There are limitations in this study including the retrospective design and a small number of patients. This study did not evaluate long-term clinical outcomes or compare the treatment strategy with other techniques. Further studies are required for this purpose.