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THA (Total hip arthroplasty) in advanced grade (grade 4) avascular necrosis (AVN) is a challenge to the treating surgeon as it affects young patients who have high functional demands and increased dislocation risk. The aim of the study was to evaluate the efficacy, survivorship, and dislocation rate of uncemented dual mobility cups (DMC) in advanced grade IV AVN young patients.
Methods
Retrospective cohort study involving 204 DMC THA for advanced grade IV AVN from January 2013 to December 2015. The sample size of the study was estimated to be 188 hips with an α error of 0.05 and β error of 0.2. Inclusion criterion was patients less than 55 years of age with advanced grade IV AVN. Patients >55 years of age, patients diagnosed with primary osteoarthritis of the hip and hip fracture were excluded from the study. 172 patients (32 with bilateral & 140 with unilateral affection) with 204 DMC THA were evaluated clinically by Harris Hip Score (HHS) and radiologically at a follow up of 60 months. P value < 0.05 was considered significant.
Results
Mean age of the patients was 42.5 ± 5.3. Preoperative HHS was 50.6 ± 10.5. Postoperative HHS at 5 years follow up was 96.4 ± 2.6. None of the operated patient had any dislocation episode or had undergone hip revision surgery (statistically significant against historical control of 2%, p value = 0.042). The radiological evaluation at 5 years showed no signs of radiolucent lines, periprosthetic osteolysis, polyethylene wear and signs of displacement or migration of the DMC. Cumulative survivorship rate at 5 years follow up was 100% without any revision/dislocation.
Conclusion
Use of DMC THA in young, advanced grade IV AVN patients was found to be a reliable option showing excellent early functional results with no dislocation. Ongoing follow up of this cohort is required to confirm the maintenance of these excellent functional results at follow up in the long term.
The etiopathology of the ONFH (Osteonecrosis of the femoral head) is disruption of blood supply to the femoral head thereby causing cellular death of the bone tissue. This results in mechanical failure when loaded thereby causing deformation of the femoral head. End stage Osteonecrosis of the femoral head is characterized by articular collapse with resultant incongruence and severe arthritis of the hip joint.
The commonly followed classification of the ONFH is the one proposed by FICAT and ARLET. In stage 1 the radiological appearance is normal. In stage 2 the femoral head shows cystic or sclerotic changes. Stage 2 is further divided into stage 2 A: no crescent sign and stage 2 B: subchondral collapse (crescent sign) without flattening of the femoral head. Stage 3 has flattening of the femoral head and stage 4 shows osteoarthritis of the hip joint with decreased joint space and articular collapse. Early stages of ONFH are managed with conservative treatment.
The treating surgeon faces a problem in doing THA in these ONFH patients because the majority of these patients are young and have high functional needs and expectations. THA in ONFH is shown to have inferior clinical outcomes as compared to THA in primary osteoarthritis of the hip joint. The complications like THA dislocation, revision and infection are more common in ONFH.
These etiologies of ONFH are also an independent risk factor for dislocation and complications post THA in ONFH. According to the AJRR (American Joint Replacement Registry), the most common cause for THA revision is THA dislocation (17.3%) much ahead of infection and fractures.
The causes of THA dislocation are patient specific (age, sex, quality of muscle) and operative procedure related(type of surgical approach, positioning of the components and femoral head diameter).
Hence it is extremely important that a surgeon carefully choses a THA implant for these young active high functional demands ONFH patients which will provide additional stability, better mobility and better long term survival.
In 1974, Gilles Bousquet devised dual mobility cup combining the principles of Sir John Charley's low friction Arthroplasty with that of large head concept of MacKee Farrar. This implant offers higher range of mobility with a low dislocation rate.
A comparative and retrospective study of three hundred and twenty primary Charnley type hip replacements with a minimum follow up of ten years to assess whether a dual mobility cup has a decreased dislocation risk.
Early polyethylene wear leading to intra prosthesis dislocation, poor means of bone fixation, and iliopsoas impingement were all issues with the first-generation dual mobility cups.
The second and third generation of DMC has not reported the complications seen with the first-generation dual mobility cups because of improved geometry of the implant and better surface finish for bony fixation.
showed a 100% survival of THA with DMC at 10 years in young active high functional demand patients with ONFH. The purpose of the present study is to study the safety and efficacy of the third generation DMC THA in young active high functional demand patients with ONFH.
2. Materials and methods
It was a retrospective cohort study involving all the eligible cases (204 DMC THA for advanced IV grade AVN) from January 2013 to December 2015. Sample size was estimated to be 188 hips with α error of 0.05 and β error of 0.2 (for 90% reduction in the rate of dislocation with fixed bearing i.e. 3.2%). Inclusion criterion was patients with advanced grade IV AVN less than 55 years of age (chronological age). Patients >55 years of age, patients with primary osteoarthritis of the hip and hip fracture were excluded from the study. One hundred and seventy two patients (32 with bilateral & 140 with unilateral affection) with 204 DMC THA were evaluated clinically by Harris Hip Score (HHS) and radiologically at a follow up of 60 months. The study had ethics committee approval of the participating institutes. All the surgeries were performed by the same surgical team. The posterior approach was used for the DMC THA. All the patients received hydroxyapatite coated uncemented femoral stem and press fit 3rd generation uncemented DMC [Fig. 1]. In the third generation DMC, The alumina coating on the first generation cup was changed to plasma-sprayed titanium and hydroxyapatite bilayer coating. This was done to improve bone integration and cup fixation. The third generation DMC has a denser, gamma irradiated polyethylene liner. Also to avoid jamming of the inner and outer surfaces of the liner, the clearances have been altered. These modifications are done to prevent polyethylene wear, aseptic loosening and intra-prosthetic dislocation. Pre-operative X-rays were taken [Fig. 2]. All the patients received three doses of intravenous antibiotics. All the patients were mobilized full weight bearing with the help of walker on the second post-operative day. Thromboprophylaxis was in the form of injectable low molecular weight heparin (0.6 ml subcutaneously once a day) for the first two days post-operative followed by 10 mg of oral rivaroxaban once a day for 6 weeks. All the patients had a minimum follow up of five years after the indexed DMC THA. The patients were clinically, functionally, and radiologically assessed by an independent observer who was not part of the operative team. The Harris Hip Score was used to evaluate the functional clinical outcome. Annual post-operative X-rays (Anteroposterior and lateral views) were used to detect radiolucent lines at the implant-bone interface, tilting or movement of the DMC, and the presence of osteolysis around the prosthesis, which could indicate implant loosening [Fig. 3, Fig. 4].
Statistical analysis: The results were expressed as means±standard deviation or as percentage. Cumulative survival rate was assessed by taking the end point as acetabular and femoral component revision for all causes.
3. Results
Two hundred and four DMC THA (172 patients with 32 bilateral and 140 unilateral THA) were studied. The pre-operative patient characteristics are shown in Table 1. The ceramic on plastic articulation was used in 82% of hips (n = 167) the metal on polyethylene articulation was used in 18% of hips undergoing DMC THA (n = 37). The commonest etiology was idiopathic followed by steroid intake and alcohol consumption. The mean operative time was 84.50 ± 9.50 min. The mean operative blood loss was 115.50 ± 14.50 cc which was measured by the anaesthetist. The hospital stay was 3.50 ± 1.50 days. The mean follow up was 67.50 ± 11.50 months. There was not a single case of dropout at five years follow up. The pre-operative HHS improved from 50.6 ± 10.5 to 96.4 ± 2.6 at five years follow up (statistically significant p value < 0.05). The radiological assessment on the x rays done at five years post-operative follow up did not show any signs of loosening in the form of tilting or migration of the DMC, appearance of radiolucent lines around the implants and periprosthetic osteolysis. All 172 patients had gone back to their normal activities like running, jogging, squatting and sitting cross legged [Fig. 5]. There was no episode of dislocation in any of the 172 patients (204 hips) at five years follow up. The cumulative survival rate was 100% at five years follow up [Table 2]. There were four complications in our cohort. Two patients had superficial wound infection which was managed by incision debridement and secondary suturing. The other two patients had post-operative urinary tract infection which was treated with appropriate oral antibiotics as per the urine culture and sensitivity report.
Table 1Pre-operative patient characteristics.
Number of Patients: 172
Number of THA: 204
Age (Years, Mean ± SD)
42.5 ± 5.3 (Range: 37–48)
Sex ratio
128(M): 44 (F)
Etiology
Idiopathic
75 (36.76%)
Alcohol
62(30.39%)
Steroids
55(26.96%)
Others (Sickle cell disease, HIV meds, Systemic lupus erythematosus)
The THA in patients with ONFH is a challenge to the operating surgeon as it has increased incidence of complications and poor long-term survival. The earlier first-generation THA implants have shown >30% failure at ten years follow up.
The concerns associated with the use of DMC THA in young patients as against conventional THA are increased cost, increased polyethylene wear, aseptic loosening, potential metal corrosion and increased metal ion levels. The DMC concept has evolved overtime since it was first introduced by Bousquet. In the third generation DMC, which we used in this cohort of patients, the cup has hydroxyapatite bilayer coating to improve bone integration and cup fixation. It has a denser, gamma irradiated polyethylene liner. To avoid jamming of the inner and outer surfaces of the liner, the clearances have been altered. These modifications are done to prevent polyethylene wear, aseptic loosening, intra-prosthetic dislocation and prevent potential metal corrosion. With the advent of cementless fixation and improved articulation (ceramic on ceramic or metal on highly cross-linked polyethylene) the ten-year survival rate has improved to about 90% in these young ONFH patients.
also found higher revision rates in THA for ONFH than for primary osteoarthritis. These higher revision rates were despite using the newer generation improved prosthesis. Dislocation features as the dreaded post-operative complication in these young active high functional demand patients. Dislocation is also the most important cause of early failure and revision in young patients after THA.
studied a cohort of 207285 THA patients operated between 2011 and 2014. It showed the AVN to be a definite risk factor for post-operative dislocation. The odds ratio (OR) was found to be −1.67 (95% CI, range, 1.45–1.93 with p value < 0.0001. Kunutsor et al.
in their study did meta-analysis of 125 studies involving approximately five million hip replacements for determining the risk factors for dislocation after primary THA. Their study showed AVN to be a definite patient related risk factor for dislocation/instability. The risk ratio, RR was 1–71 (95%CI) with a range of 1.35–2.18. Ancelin et al.
Total hip arthroplasty survival in femoral head avascular necrosis versus primary hip osteoarthritis: case-control study with a mean 10-year follow-up after anatomical cementless metal-on-metal 28-mm replacement.
J Orthop Traumatol: Surgery & Research.2016; 102: 1029-1034
in a study of 282 patients (149 AVN and 133 primary osteoarthritis) found that the revision for dislocation was higher in AVN group than the primary osteoarthritis group (8 in AVN group vs. 1 in primary osteoarthritis group, p value 0.031). Also recent studies have demonstrated superior results of DMC THA over fixed bearing THA in AVN. Rowan et al.
studied 136 patients (age <55 years) in each group who underwent primary DMC THA and fixed bearing THA. At 3 years follow up they reported no dislocation, intra prosthetic dislocation in DMC group whereas there were 7 dislocations (5.1%) in the fixed bearing group. Two out of 7 dislocations in the fixed bearing group required revision. There was no difference in the modified Harris Hip Score at mean 3 years follow up between the two groups. Dubin et al.
performed 27 multicentric retrospective reviews of 664 DMC and 218 fixed bearing THA. The mean follow up was for 2 years. There was no dislocation in DMC group and there were 2 dislocations in the fixed bearing group. The HHS and SF-12 physical components score in DM group was better than fixed bearing group (91.44 vs. 87.81, p value 0.006 and 46.83 vs. 41.55, p value 0.015 respectively). In view of this emerging new evidence, we chose to perform DMC THA in this cohort of patients (patients<55 years of age) with stage 4 Ficat-Arlet AVN of the hip. Studies by Agarwala S et al. and Agarwala Sanjay et al.
have demonstrated an excellent track record of the implant type used in our study. Both these studies reported excellent patient reported outcome measure (Harris Hip Score). Our survival rate of 100% is better if not equal to the reported survival rate in the studies of Schmolders
(32 mm ceramic on polyethylene articulation THA in patients <50 years of age with all etiologies, 96.8% survival) and Bedard (patients with advanced ONFH, 93% survival).
We did not encounter any dislocation in our series.
Our study has certain limitations. The first limitation is short follow up of 5 years. This short follow up may be premature to detect osteolysis, aseptic loosening and intraprosthetic dislocation. We are continuing to follow up this cohort of patients to see whether these early good results maintain over a period of time. The second limitation is the retrospective nature of the study. But this limitation is offset by the large cohort of 204 hips with not a single case of dropout at five years follow up. The third limitation of the study is that the cohort consisted of ONFH patients of Indian ethnicity. In future similar studies should be undertaken and data should be captured for other diagnosis (indication for THA) and in other ethnicity patients.
The strength of our study is to the best of our knowledge; it is the first large cohort case series of DMC THA in young active high functional demand ONFH Indian/Asian patients.
5. Conclusion
The study shows early encouraging results of the use of DMC THA in young active high functional demand grade IV ONFH patients. Further continuous follow up of this cohort is required to see the sustainability of these early results at a longer follow up.
Funding
No funding was received for the study.
Ethics approval
Local ethics committee approval was obtained before the study. Also, all patients consented to participate.
Consent for publication
We hereby give our consent for publication.
Authors' contribution
All authors have contributed equally to the preparation of the manuscript.
Availability of data and materials
This published article contains all the data generated or analyzed during this study.
Previous presentation
The study data was presented as an E Poster at the American Association of Hip and Knee Surgeons (AAHKS) meeting 11–14THNovember 2021 at Dallas, Texas, USA.
Funding
There is no funding source.
Informed consent
Informed consent was obtained from all individual participants included in the study.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests.
Abbreviations
THA
Total Hip Arthroplasty
AVN
Avascular Necrosis
DMC
Dual Mobility Cups
ONFH
Osteonecrosis of the Femoral Head
References
Mwale F.
Wang H.
Johnson A.J.
Mont M.A.
Antoniou J.
Abnormal vascular endothelial growth factor expression in mesenchymal stem cells from both osteonecrotic and osteoarthritic hips.
A comparative and retrospective study of three hundred and twenty primary Charnley type hip replacements with a minimum follow up of ten years to assess whether a dual mobility cup has a decreased dislocation risk.
Total hip arthroplasty survival in femoral head avascular necrosis versus primary hip osteoarthritis: case-control study with a mean 10-year follow-up after anatomical cementless metal-on-metal 28-mm replacement.
J Orthop Traumatol: Surgery & Research.2016; 102: 1029-1034
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