Hip resurfacing: Selection criteria and results of 423 consecutive hips at 5 years

L Kohan, R Cordingley, D Kerr (Joint Orthopaedic Centre)

Introduction:

This is a descriptive, prospective, longitudinal analysis of functional outcomes and component survival in 423 hips (393 patients). A consecutive series over 5.25 years with all implants the Birmingham-MMT hip resurfacing device. An overall 98.4% implant survival rate was achieved, with 100% survival in patients under 65 years.

Method:

Selection criteria were bone mineral density, activity level and co morbidities. Age was not a selection criterion. No patient was lost to follow-up.  The age range for the hip resurfacing components was 24 – 87 years, with 325 males and 98 females.  The average age was 54 years. There were 339 patients under 65 years of age, 264 males and 75 females. In the group over 65 years of age and over there were 61 males and 23 females. 11 patients had previous osteotomy.  SF-36, Womac Health Questionnaires, Tegner activity scores and BMD assessment, completed and analysed.

Results:

Total survival was 98.4%. Patients aged less than 65 years demonstrated a 100% survival while patients aged 65 and over showed a cumulative survival rate of 92.8%.  429 hips (393 patients) were resurfaced with a mean elapsed time since re-surfacing of 26.6 months (maximum 64 months). 1 patient died with a fully functioning prosthesis. 7 hips were revised due to femoral neck fracture. Of these two men had high alcohol intact and one was a woman on long term Dilantin treatment. 3 males fractured due to trauma. Two transient nerve palsies, seven asymptomatic DVT’s and one hip dislocation following a fall. SF-36 and WOMAC scores were assessed preoperatively, 6, 12, 24, 48 months post operatively. The patients were divided into 4 groups males and females over and under 65. All groups showed improvement in function, pain, stiffness, social functioning, physical function and physical role. Males under 65 had the greatest improvement overall. Tegner activity scores showed 72% of patients scored 3 or under. 12 months after surgery 87% scored 3 and over. BMD assessment was introduced after the first 4 fractures. A t-score of less than -2.0 preoperatively excluded the patient from resurfacing

Conclusion

While this is an early analysis of outcomes for primary hip resurfacing, we observed an overall rapid improvement in recovery, mobilisation and return to normal activities over a 5.25 year period.  The above selection criteria were useful in minimising femoral neck fracture.