Radiological Monitoring of Hip Replacements in Sickle Cell Disease Patients : Report of 31 Cases

Aim: The objective of the study was to report the progressive complications of hip joint disease in a population of sickle cell. Materials and Methods: A descriptive and retrospective study from 2002 to 2008: A case of 31 sickle cell subjects having presented an advanced osteonecrosis of the femoral head. All the patients benefited from an arthroplasty in adulthood with a radiographic monitoring in immediate post operative before and after one year. The sickle cell subjects were compared to a non sickle cell control group of 37 patients according to the same criteria. The analysis had included considerations of the environment and the position of the prosthetic parts, as well as additional modifications. The types of complications and the moment at which they occur were indexed and analyzed using a statistical test of FISHER with a threshold of significance level p < 0.05. Results: The average age of sickle cell patients was 35 years and non sickle cell disease sufferers, 51, with a male predominance. Indications for surgery were dominated by coxarthroses, 31 cases (100%) in sickle cell disease sufferers and 17 cases (46%) among the control group. All our patients underwent a radiological control in the immediate postoperative. They were fewer between 6 months and 1 year (19%). The immediate complications were dominated by fractures 2 cases in non sickle cell disease sufferers. The complications before one year were marked by a predominance of dislocation, 3 cases in the non sickle cell population against 2 cases in sickle cell population. The loosening were the most observed complications in both populations after a year and more (5 cases in sickle cell disease sufferers and 6 cases in non sickle cell disease sufferers). Conclusion: The evolutionary complications of joint replacements in sickle cell subjects are not more frequent than in non sickle cell subjects.


Introduction
Sickle cell disease, the most frequent hemoglobinopathy in the world, occurs primarily in black patients and populations around the Mediterranean.It is about a genetic disease characterized by the presence of S hemoglobin, transmitted according to the Mendelian autosomal codominant way.
The sickle cell disease diagnosis is due to the hemoglobin electrophoresis which makes it possible to differentiate the abnormal hemoglobin: AS, SS, SC, S beta thalassemia [1].Sickle cell disease affects approximately 10% of the population of Côte d'Ivoire.It is a provider of hip disease in young patients among 20% -32% [2] of sickle cell disease sufferers.The management of these hip diseases often requires the completion of a joint replacement.The environment, the relative youth of these patients and the quality of bone pose the problem of the feasibility and the survival of hip implants [3].Finding the evolutionary complications and evaluating the morbidity of hip replacements in sickle cell patients are the objectives of this work.

Materials and Methods
This was a retrospective study that took place in the service of radiology and trauma surgery of the International Polyclinic Sainte Anne Mairie (PISAM).
We collected 31 cases of sickle cell patients known since childhood, who presented the court monitoring their sickle cell disease advanced arthropathy of the femoral head who underwent hip replacement between 2002 and 2008.
The inclusion criteria: about age greater than or equal to 21 years, who has made control of X-rays; the average age of patients was 35 years with extremes of 25 and 45.
The exclusion criteria: about age below 21 years, or adult subject who did not receive all the postoperative radiographic inspection.
In order to assess the morbidity of this intervention in the sickle cell patient, we studied a control population of 37 adult patients without sickle cell disease and who received a hip replacement in the same structure during the same period.
The type of prosthesis has not been taken into account in the development of complications.
The average age of the pilot population was 51 years, with extremes ranging from 40 to 92 years.
The total hip prosthesis was the most used in our patients in 68% of the cases followed by cervical-cranial prosthetics 29% of the cases and in 3% of the cases, an intermediate prosthesis.
The cement was the method of attachment used in almost all the cases (95%).
Face basin impacts, 3/4 wing and shutters were carried out in each immediate postoperative radiological control at 6 months, 12 months and annually.
The monitoring time was 10 years for the first and last patient operated.
The analysis of the radiological materials had comprised: 1) The analysis of the environment, the position and integrity of the prosthetic pieces 2) The assessment of the aspect of the femur and the acetabulum, 3) The study of soft tissue and pelvic excavation.
The type of acute or chronic complications and their moment of occurrence have been identified in each population.
The statistical analysis had been carried out using the comparative test of Fischer with a significance level P < 0.05.

1) The radiological monitoring
All our patients had received a radiation monitoring in the immediate post-operative.They were 43% to be present at the 6 months control.They were fewer between 6 months and 1 year (19%) and (24%) after 1 year.
2) The immediate complications They were observed in the immediate postoperative period and before three (03) months.They were dominated by fractures; 02 cases observed only in non-sickle cell disease sufferers.(Figure 1).A case of dislocation was diagnosed in each population.
The presence of cement was highlighted in the pelvic cavity of a sickle cell patient.

3) Complications at 6 months
There were more dislocations (03 cases) and fractures (03 cases) in the non sickle cell population (Figure 2) than in the sickle cell population with only 02 cases of dislocations (Table 1).

4) Complications after 1 Year and More
The loosening were the most observed complications in the two populations: 05 cases in sickle cell disease sufferers and 06 cases in non-sickle cell population (Figure 3).

The Quality of the Radiological Monitoring
If the immediate postoperative period radiographies were made among all our patients on the other hand, the attendance rate of the unit of Radiology declined during the subsequent radiological monitoring.They were less than half (43%) at 6 months, 19% between 6 months and 1 year and then 24% after 1 year.The low level of attendance of the Radiology unit by these patients during the monitoring had already been revealed by FOFANA [4] in a similar study.
In contrast, the observance of radiation monitoring was better in the western series with an overall estimated attendance rates of 75% -85% [5] [6].
Our patients only attended the hospital when the operated hip became painful.They should be informed about the importance of the radiological monitoring of replacements and that any poor adherence thereof compromises the survival of the prostheses.
Moreover the patients' lack of financial means and the absence of health insurance in our country did not favor a good radiological monitoring and this describes the African specificity.

The Radiation Monitoring
The immediate complications were dominated by fractures and dislocations also more frequent in non-sickle cell population as well as in sickle one.They are not therefore only related to the sickle cell environment.
The causes according SEDEL [7] are of several types.There may be technical errors caused by the excessive milling of the bone pieces in connection to inadequate prostheses, the osteoporosis in the old subject, and the mechanical constraints being exerted on the prosthesis in the young patient.
The loosening with 13.50% in non-sickle cell population and 12.90% in the sickle cell population constituted the most frequent chronic complications.The statistical comparison of this complication was not significant (P = 1).
In addition, this complication was not more common among us than in Western series in which loosening up 15% to 20% of complications [8] [9].
We observed in our study a case of septic loosening in each population that occurred in an immune-compromised environment.

Conclusions
The progressive complications of joint replacement in a sickle cell environment were not more frequent than in a non sickle subject.
The high cost of prosthetics in our context remains an obstacle to the practice of joint replacements in sickle cell patients.It remains technically difficult requiring thus a perpetual monitoring.

Table 1 .
Distribution of complications in 2 populations before 1 year.

Table 2 .
Distribution of complications after 1 year.