Short term outcome of primary un-cemented total hip arthroplasty in osteonecrosis of femoral head

INTRODUCTION

Osteonecrosis of femoral head (ONFH) is characterised by cell death in the subchondral bone caused by abnormalities of blood flow to the femoral head. Chandler called it ‘The Coronary Disease of Hip’.¹ ONFH affects young adults in third to fourth decade of life.² About 5% to 13% of arthroplasties are performed yearly for ONFH in United States.³ Disease usually affects males more than females. ONFH encompasses various radiographic stages grossly divided into pre-Collapse and Collapsed head stages. Management of ONFH is defined by the stage of the disease. X-ray and MRI are used as the diagnostic tools. Groin pain, limp and support for ambulation are the common presentations. Ficat et al classification is the commonest system used for grading of ONFH.⁴ Stage 1 and 2 are managed with head salvage. Advanced stages 3 and 4 are best managed with total hip arthroplasty (THA). Proximal femoral osteotimies delay the arthroplasty in young patients with less than 30% head involvement in the weight bearing area.⁵ Despite the avantages of bone stock preservation and deaying THA, results of head - resurfacing have been discouraging.⁶ Although cemented THA was reported to have better outcome compared to un-cemented THA, recent reports suggest improved results of un-cemented THA in ONFH patients.⁷ Un-cemented THA has the advantages of less risk of infection, aseptic loosening and zero incidence of bone cement implantation syndrome.⁸ This study was performed to evaluate short-term outcome of uncemented THA in unilateral ONFH.

METHODS

This prospective interventional study was conducted in SKIMS medical college hospital, Bemina Srinagar from February 2018 to February 2020. 25 patients meeting the inclusion criteria were admitted to SKIMS MC hospital. All the patients were operated after pre-operative workup by the same surgeon via the same approach (posterolateral hip approach) after getting approval from institutional ethical committee. The implant used was same in all patients. Fully hydroxyl-apatite coated stem and pinnacle shell with metal on polyethylene interface was used. Post-operative management included intra-venous antibiotics and thrombo-prophylaxis. Patients were ambulated in the immediate post-operative period with partial weight bearing with walker with progression to full weight bearing at 6 weeks⁹. Standard hip precautions were advised. Radiographs were taken in immediate post-operative period, 6 month and 1 year follow up. Follow up was done at 2 weeks, 3 months, 6 months and final follow up at 1 year. Harris hip scoring was done preoperatively and at final follow up.

Inclusion criteria

Age- above 20 years; sex- all sexes. Osteonecrosis head femur; FICAT ARLET stage 3 and 4; DORR A and B Femori; unilateral osteonecrosis.

Exclusion criteria

Age- below 20 years; FICAT ARLET stage 1 and 2, DORR C Femori. Any medical contraindication to surgery; fresh trauma to the affected side.

Stastical analysis

Data was entered on microsoft excel software and analysis was done with SPSS version 20.0 software.

RESULTS

The study patients were in the age group of 28 to 65 years with mean age of 50.64 years. 13 females and 12 males were studied. 16 patients had left hip involvement and 9 patients had right hip affected. 11 patients had post traumatic ONFH with 8 patients post neck femur fracture and 3 patients post acetabulum fracture with hip dislocation. 9 patients had idiopathic, 3 had steroid induced, 1 with renal transplant and one patient with chronic alcohol intake. Limb length discrepancy (LLD) was found postoperatively in 13 patients. All the patients with LLD had less than 1.5 cm of discrepancy. 2 patients were complicated with superficial surgical site infection, 3 with anterior thigh pain and 1 with trendelenburg gait. Most common head size used was 36 mm in 14 patients, 32 mm in 9 patients and 28 in 2 patients. 21 patients had central stem configuration with varus in 4 patients. Acetabular inclination range from 40 to 50 degrees in all patients. Mean pre-op Harris Hip Score (HHS) improved from 65.875 to 96.52 post-operatively. Noted improvements occurred in pain score from 26 in the pre-op group to 43.04 in the post-op group. No dislocations were reported in our study and no cases of heterotopic ossification were reported.

DISCUSSION

The age group in our study ranged from 28 to 65 years with mean age of 50.64 years which points to delayed diagnosis and presentation to an Arthroplasty centre. The mean age of our study is comparable to other studies conducted on patients with avascular necrosis of the femoral head because AVN is primarily a disease of young adults.^7,8,10,11 Our study group comprised of 13 females (52%) and 12 males (48%). The gender ratio in our study correlates poorly with other studies which may be due to small sample size and more female patients with AVN presenting to hospital OPD during the study period. More than half of the arthroplasties were done on the right hip. The study group comprised of 64% involvement of right hip and 36% of the left hip joint. This is comparable to other studies.^11,12 Our study group comprised of both post-traumatic as well as non-traumatic AVN of femoral head. The study group of 25 patients include 36% idiopathic, 44 %post-traumatic, 12% steroids, 4% alcoholism, and 4% other causes. The major etiology of AVN of the femoral head in our study is contributed by the idiopathic and post-traumatic group. Two patients reported with superficial surgical site infections which cleared upon repeated antiseptic dressings (ASD). None of the patients had deep infection or continuous discharge from the incision site. This was comparable to the study of El-etewy and was slightly higher than other studies.^11,14,15 In our study three (12%) patients presented with thigh pain, two of which had varus configuration of femoral stem. This correlates closely with the study of Shah et al.¹¹ Lewinnek et al used a pelvic co-ordinate system with anterior pelvic plane in order to define the so called “safe zone”.¹⁶ They suggested a 40 average acetabular inclination angle. Hirakawa et al suggested an inclination angle of less than 40 is associated with better long-term results as compared to an angle of 45 or above.¹⁷ The mean acetabular inclination angle in our study was 45.24 degrees ranging from 43 to 49 degrees which is comparable to other studies.^8,15,18 Femoral stem was placed in central position in 84% of the patients, 16% had slightly varus position of the femoral stem at final follow-up. None of the patients had valgus configuration of the femoral stem. This correlates well with other studies.^8,15 The average Harris hip score (HHS) improved from 65.875 in the pre-op group to 96.52 at the final follow-up in post-op group. The improvement was grossly seen in the pain scores which improved from a mean score of 26 in pre-op group to 43.04 in the post-op period at final follow up. The improvement in HHS was comparable to other studies.^12,14,15,18 The grading of outcome based on the improvement in HHS showed 96% graded as excellent while 4% were graded as good. The grading of outcome in our study was in line with the studies.^12,18-20 In our study there were no dislocations with the posterolateral approach and posterior soft tissue repair. Kim et al reported three dislocations in his study which were attributed to the use of 22 mm head and habitual squatting on floor.⁸ None of the studied patients had any evidence of heterotopic ossification at final follow-up.

CONCLUSION

Avascular necrosis of the hip is the disease of young adults. Advanced stages characterized by flattening of articular surface of the femoral head with secondary arthritis are responsible for the limp and loss of range of motion of hip joint. Total hip arthroplasty is the only treatment that relieves pain and restores mobility of the hip joint in advanced stages of AVN. Our study used uncemented fully hydroxyapatite coated femoral stem (corail) with porous coated acetabular shell with metal on polyethylene interface. Our study despite some complications showed favourable short-term results in advanced stages of AVN of head of femur.

ACKNOWLEDGEMENTS

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

REFERENCES

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