External fixation assisted reduction in the treatment for obsolete hip dislocations with limb discrepancy

Abstract Background: The purpose of this study is to evaluate a new method for treating obsolete acetabular dislocation with limb discrepancy by external fixation assisted pre-reduction. Methods: Thirteen patients admitted from January 2010 to February 2018 with a mean duration from injury to surgery of 5.0±2.1 months and an average preoperative leg-length discrepancy of 7.7±2.3 cm were enrolled in this study. The dislocation and associated acetabular fracture type, clinical outcomes and residual limb equality were evaluated. Results: All patients were posterior dislocations and nine presented with acetabular fractures and were followed-up at least 12 months. The average traction duration of external fixators was 28.8±8.0 days and all patients received second-stage open reduction and internal fixation. Six patients showed residual limb discrepancy within 2 cm. Patients showed significant improvement in hip function and pain relief. Complications including avascular femoral head necrosis and osteoarthritis occurred in 3 patients. Conclusion: Effective correction of limb discrepancy and improved function showed in patients with obsolete acetabular dislocations and limb equality using traction by external fixation combined with second-stage open reduction. The long-term outcomes need continued follow-up.

and limited function of hip joint. For patients with obsolete fracture, callus formation and adhesion caused by connective tissue make regular reduction difficult. The common treatments reported in previous studies for obsolete hip dislocation included skeletal traction and total hip arthoplasty. [6,7] Here we propose a new surgical strategy to obsolete acetabular dislocations by using external fixators in preoperative traction. The aim of this study is to discuss the feasibility of this operation method.

Patients And Methods
We reviewed all patients with old hip dislocation treated with external fixators in our department from January 2010 to February 2018 and 13 patients were enrolled in this study. Permission for this study was obtained from the Medical Ethics Committee of authors' institution and written informed consent was obtained from every patient. All patients suffered posterior dislocation and the classification was described by Thompson and Epstein.
[8] The associated acetabular fracture was classified by Judet-Letournel. [9] The function of hip joint was evaluated using modified Merle D'Aubigné and Postel [10] scoring system. Residual pain was assessed according to visual analogue scale (VAS).

Surgical procedures
First-stage traction by external fixation: surgeries were performed on patients under regional anesthesia. Two incisions about 1cm were made on the iliac crest and lateral thigh. Two screws were placed in anterior inferior iliac spine and another two screws were placed in femur mid-diaphysis under fluoroscopic guidance. Then a monolateral external fixator was connected. (Fig 1) The traction procedure began 3 days after the surgery with external fixator stretching 1 to 3 mm a day. Plain X-ray radiogram was taken every 5 to 7 days to examine the reduction. Traction stopped when femoral head was drawn beneath the articular surface of the acetabulum.
Second-stage open reduction: after the first-stage traction, open reduction was operated under general anesthesia. A Kocher-Langenbeck (K-L) approach or combined approaches of ilioinguinal and K-L were used. After the incision of articular capsule, exposed hip joint space, cleared fibrous tissue and intra-articular fragments, reconstructed and fixed acetabulum, then reducted femoral head.
Postoperative skeletal traction was used according to condition of open reduction.

Results
Thirteen patients were enrolled in this study with 5 female patients and 8 male patients.
The average age was 36.7±10.5 years (range, 19-49 years). Nine patients were associated with acetabular fractures and the pattern of fracture and posterior dislocation are shown in Table 1. The mean duration from injury to surgery was 5.0±2.1 months (range, 2.5-9 months). The mean preoperative leg-length discrepancy was 7.7±2.3 cm (range, 5-12.

Discussion
Neglected traumatic hip dislocations are rare in in adults. High-energy trauma are often associated with multiple injuries including abdominal organs and lower limbs. [11] The urgent of maintaining hemodynamic stability and to handle combines injuries may cause delayed diagnosis and treatment of fracture and lead to obsolete hip dislocation. Also some patients stopped seeking medical help or attended hospital many days after trauma because of financial strain, especially in developing countries. [11] Skeletal traction is important in joint reduction. The common used traction techniques for hip joint include skin, halo-femoral and tibial tubercle traction. It usually takes two to three weeks for skin traction with a traction weight under 5kg otherwise complications like skin break or vesicles may occur. Though halo-femoral and tibial tubercle traction can carry more weight but often end with unsatisfied results in patients with neglected hip dislocation. Pai and Kumar [12] reported heavy traction and abduction conducted for eight patients with neglected posterior dislocation and only four of them achieved concentric reduction.
Gupta [6] used traction of seven to eighteen kilograms for five to seventeen days which allowed over-reduction of the dislocation and the then gradually reducted the femoral head into the acetabulum by reducing the traction and abduction but failed to reduct dislocation with a duration for more than two months. For patients who had neglected hip dislocation, prolonged dislocation may cause severe joint contracture. It's difflicult to achieve satisfied reduction by regular traction. Also heavy traction may lead high risk of neurovascular complications.
Distraction osteogenesis by external fixators has been widely used in patients with bone defects. [13] The good extension and regeneration ability of skin and bone offers theoretical basis of the application of external fixators in traction reduction. Screws were placed in anterior inferior iliac spine and ipsilateral femur mid-diaphysis to assemble the external fixator. The daily lengthening was about 1 to 3mm and could be suitably increased according to patients' tolerance. Plain radiograph was routinely taken regularly to examine the correction of shortening. Though shortening could be effectively corrected through traction by external fixators, it was hard to achieve accurate reduction and the associated acetabular fracture which occured in 10 patients also needed surgical repair.
Open reduction was performed when the femoral head was reduced underneath the articular surface. At this time, with muscle stiffness alleviated and the surgery was done with less invasiveness and reduced duration. arthritis. [14] Previous studies reported the incidence rate of arthritis was 16.1% to 30.0% and 8.1% to 10% of AVN in the mid-to-long-term follow-up. [1,15] In our patients, AVN occurred in 2 patients (15.4%) and osteoarthritis occurred in 1 patient (7.7%). Scholars also reported that complications usually developed within 5 years of dislocation [11,16], our study only reports a short-term follow-up result within 18 months. As the incidence of secondary complications may increase with time [17], the accurate complication rate should be recalculated in the long-term follow-up. (excellent and good results). Limb discrepancy was effectively corrected and no patient was left more than 2 cm inequality laying the foundation for possible THR in the future.
Though AVN and arthritis occurred in 3 patients, none of them received further treatment at the last follow-up. The clinical efficacy of two methods should be compared in a more convincing case control study and a long-term follow-up.
From our experiences, external fixation was effective for pre-reduction in patients suffered old acetabular fractures with limb discrepancy, but still several contraindications are noteworthy. First, it shouldn't be used in patients with heterotopic ossification, which most commonly occurs in hip joint and the incidence after traumatic dislocation was 32% to 37%, [21,22] for traction would be resisted by ectopic bone. As the fixation technique need stable anchors, it is unfit for patients with unstable pelvic ring or femur. Also

Availability of data and materials
The data used in the current study are available from the corresponding author on reasonable request.  I  13  Good  0  3  9  No  I  18  Fair  1  4  5.5  No  I  14  Good  0  5  3  Posterior wall  I  15  Excellent  0  6  8  Posterior wall  II  17  Poor  2  AVN  7  4  Transverse  with posterior  wall   II  17  Fair  3  AVN   8  3  posterior wall  II  15  Good  0  9 2