|Year : 2020 | Volume
| Issue : 3 | Page : 247-253
Dual mobility total hip arthroplasty in patients at risk for dislocation
Mohamed M.M Mahmoud
Department of Orthopedics and Traumatology, Faculty of Medicine, Al-Azhar University, Assiut, Egypt
|Date of Submission||27-Mar-2020|
|Date of Decision||16-May-2020|
|Date of Acceptance||25-Jun-2020|
|Date of Web Publication||30-Oct-2020|
Mohamed M.M Mahmoud
Department of Orthopedics, Al-Azhar University Hospital, Assiut, 71511
Source of Support: None, Conflict of Interest: None
Background Total hip arthroplasty (THA) is one of the most successful surgeries in orthopedics. However, postoperative dislocation is one of the major complications. There are some patients with higher risk for dislocations. Dual mobility cup THA (DMC) may decrease the rate of dislocation and enhance functional outcome in those patients.
Aim The aim was to retrospectively assess postoperative rate of dislocation and functional outcome in patients with preoperative risk factors for dislocation treated by DMC THA.
Patients and methods A total of 26 DMC THAs were done for 25 patients with preoperative risk factors for dislocation. Functional outcome by Harris hip score and dislocation rates have been followed for a period of 12–48 months (mean: 31 months).
Results There was 0% rate of dislocation till the last follow-up. There was marked improvement in Harris hip score, with good to excellent results in 74% of patients.
Conclusion DMC THA is a good option for patients at risk for dislocations, with very low or no rate of dislocation, with good functional outcomes.
Keywords: dual mobility cup total hip arthroplasty, functional outcome, risk for dislocation
|How to cite this article:|
Mahmoud MM. Dual mobility total hip arthroplasty in patients at risk for dislocation. Al-Azhar Assiut Med J 2020;18:247-53
| Introduction|| |
Total hip arthroplasty (THA) is considered as one of the most successful surgical procedures in orthopedic surgery regarding pain relief and improving function of badly diseased hips ,. However, postoperative dislocation is still one of the major complications following THA and is estimated to be 7% in primary THA and 25% in revision cases . Dislocation after THA is reported to be the first cause of reoperation , which usually occurs owing to many causes, which can be divided into patient factors (old age, female patient, and primary etiology), surgical factors (components malposition and posterior approach), and design of the prosthesis (head 22.2 mm) ,. First, dislocated THA is treated by closed reduction and abduction brace; however, dislocations more than twice may be an indication of surgical intervention through correcting components’ position, using large heads or increase offset . In the past, constrained cups and bipolar were salvage treatment for recurrent dislocation with their drawbacks of low functional outcome and decrease longevity of the prosthesis ,. However, the introduction of dual mobility cup (DMC) led to its popular use in patients with higher risk for dislocation, with its advantages of increasing stability and good functional outcome . Many authors have reported lower rate of dislocation after dual mobility THA ,,.
The aim of this study was to evaluate short-term outcome of dual mobility THA in patients at risk of postoperative dislocation, focusing mainly on postoperative stability and functional outcome.
| Patients and methods|| |
This is a retrospective study on 26 DMC THAs that was done in 25 patients at Al-Azhar University Hospital, Assiut, during the period from January 2016 till January 2019. The study was approved by the ethical committee of Al-Azhar-Assiut Faculty of Medicine. All surgeries have been done by one surgeon (the author). Patients comprised 11 males and 14 females, with mean age of 65.7 years (range: 38–80 years). The preoperative diagnosis was fracture neck of femur (11 hips) in patients with high risk of postoperative dislocation (old stroke, polio, old age, female, parkinsonism, dementia, and epilepsy), acetabular protrusion after hemiarthroplasty (two hips), recurrent dislocated hip arthroplasty (three hips), failed trochanteric fracture fixation (three hips), and failed hemiarthroplasty (seven hips in six patients) owing to loosening (one septic and six aseptic) ([Table 1],[Table 2],[Table 3]). There were 14 primary THAs in 14 patients and 12 revision THAs in 11 patients.
Preoperative examination and clinical scoring by Harris hip score (HHS) were done for all patients. Preoperative radiography and full laboratory investigations were also done. Erythrocyte sedimentation rate and C-reactive protein were done for revision cases to exclude infection.
Preoperative manual templating was done for all patients. Lateral approach has been done, with the patients in the lateral decubitus position. Extended trochanteric osteotomy through lateral approach was done for two hips (in two patients). Cemented DMCs were used for all hips, except one hip, which received cementless DMC. Cemented standard stem was used for 22 hips (in 21 patients), cementless long stem in three hips, and cementless conventional stem in one hip. Trial reduction was first done and then final reduction and closure in layers. There were no intraoperative complications, except one patient with periprosthetic femoral fracture, treated by locked plate during the surgery. No postoperative complications were noted. All patients started full weight bearing in the second postoperative day except the patient with the femur fracture, who started weight bearing 3 months postoperatively. Postoperative antibiotics were given for 2 days postoperatively except one patient with second stage revision where antibiotic continued for one and half months. Low-molecular-weight heparin was given for one month postoperatively. Clinical follow-up with HHS was done at 3 months, 6 months, and then yearly. Immediate postoperative radiographs and at 3 months, 6 months, and every year were taken ([Figure 1],[Figure 2],[Figure 3]). The mean follow-up duration was ∼31.5 months (range: 12–48 months). No patient has been lost to follow-up.
|Figure 1 (a) Preoperative radiography of the hip of a 50-year-old female patient with protrusion acetabulum. (b) Postoperative radiography shows treatment by bone graft, Kerboull ring, cemented DMC, and cementless long stem. DMC, dual mobility cup.|
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|Figure 2 (a) Preoperative radiography of the hip of a 65-year-old male with failed troch. Fracture fixation after metal removal. (b) Postoperative radiography shows treatment by cemented DMC THA. DMC THA, dual mobility cup total hip arthroplasty.|
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|Figure 3 (a) Preoperative radiography of the hip of a 50-year-old male with old poliomyelitis shows fracture neck of femur. (b) Postoperative radiography shows treatment by cemented DMC THA. DMC THA, dual mobility cup total hip arthroplasty.|
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Statistical analysis of data of patients regarding age, sex, preoperative diagnosis, risk factors, and comparison between preoperative HHS with postoperative HHS of patients have been done.
| Results|| |
DMC THA was performed for 26 hips in 25 patients. The mean postoperative follow-up period was 31.5 months. Overall, 53.5% of the hips were primary hip arthroplasties and 46.5% were revision hip arthroplasties. There is marked clinical improvement, where the mean HHS was 11.8 (range: 9–30) preoperatively, and became 78.6 (range: 65–90) postoperatively, with excellent results in four (15.38%) hips, good in 18 (69.23%) hips, fair in two (7.6%), and poor in two (7.6%) hips. The rate of postoperative dislocation is 0%. There was one intraoperative periprosthetic femoral shaft fracture ([Table 1],[Table 2],[Table 3],[Table 4],[Table 5] and [Figure 4],[Figure 5],[Figure 6],[Figure 7]).
|Table 4 HHS score of the studied patients in preoperative and postoperative|
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|Figure 6 Comparison between preoperative and postoperative mean HHS of patients.|
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| Discussion|| |
This is a retrospective study on consecutive 26 DMC THAs in 25 patients at risk of postoperative dislocation. In this series, no postoperative dislocations have been documented in any patients through the whole follow-up period, which ranged from 12 up to 48 months. Although all patients in this study have at least one or more risk factors for dislocation, as shown in [Table 1], there is marked improvement in HHS, with good to excellent results in 74% of patients.
Risk factors for postoperative dislocation of THA were classified into patients, factors, prosthesis factors, and surgical factors. Patient factors were sex, age, etiology, and associated cerebral or neuromuscular diseases . Females have higher risk of dislocation than males. In this series, female represented 50% of cases ,. Older age group more than 70 years have high risk of dislocation ,. In the prescribed patients, 32% of patients were over 70 years of age. Different preoperative etiologies have higher risk of dislocation such as fracture neck of femur, revision THA, and disruption of abductors ,. In these patients, 42% of the patients had fracture neck of femur, 46.5% had preoperative failed hip replacement, and 11.5% had failed trochanteric fracture fixation with avulsed greater trochanter. Associated cerebral or neuromuscular diseases, old poliomyelitis, cerebral stroke, parkinsonism, dementia, and epilepsy increase the risk of dislocation ,. Overall, 20% of the cases among these patients have neuromuscular problems.
DMC THA has been established as a solution of postoperative instability and for those patients with high risk for postoperative dislocation. This is mainly owing to the presence of two articulation points in DMC: one between the two heads (small metal and large polyethylene) and the other between the large polyethylene head and the acetabular cup .
The results of this study are comparable with that of Romagnoli et al. , who stated in their systematic review that dual mobility THR reduces the risk of postoperative dislocation even in those patients with high risk for postoperative dislocation.
In this series, DMC THA has been used for both primary and revision THA, without dislocation rates, which also coincides with De Martino et al. , who documented that DMC THA reduces dislocation rate in both primary and revision THA.
Regarding functional outcome, in the present series, all cases showed marked improvement in functional outcome, where the mean HHS was 11.8 preoperatively and became 78.6, with only two hips in two patients having poor results, owing to hemiplegia in one patients and rheumatoid arthritis affecting both knees in the other patient. Ukaj et al.  found that DMC THA gives better outcome than hemiarthroplasty in treatment of fracture neck of femur regarding functional outcome and postoperative dislocation.In the present study, only one hip was revised for recurrent dislocation of bipolar hemiarthroplasty, with more than 3 years of follow up without any dislocation. Many authors showed that using DMC THA for revision THA owing to recurrent dislocation has low revision rate ,,,,,,. Moreover, Stucinskas et al.  showed that DMC THA had lower risk of re-revision owing to dislocation and other reasons when compared with other prosthetic designs used for revision THA owing to recurrent dislocation.
The limitation of this study is the limited number of patients and the retrospective nature of the study.
In conclusion, DMC THA can be used in patients with high risk for postoperative dislocation and even with cases with recurrent dislocation with good functional outcome and very low or no rate of dislocation.
Special thanks to Professor Dr Ahmed Abdel Aal Professor of Orthopedics, Assiut University Hospital, for his support and guide in taking decision making for operating these patients.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]