[Two-year results of a modular short hip stem prosthesis--a prospective study].

AIM

The short-term results of a prospective, consecutive series of 50 cementless modular short hip stem endoprostheses are reported.

METHOD

48 cases were available for clinical and radiological follow-up at an average time of 2.4 years post-op. One patient did not consent to a follow-up investigation, 1 early revision was necessary 4 weeks post-op after a fall precipitating a periprosthetic fracture.

RESULTS

The average age at the time of THA was 54 years and the Harris hip score reached 95 points at the time of follow-up. One implant had aseptic loosening and 1 implant was revised due to a failure of the modular titanium neck adapter. An equal number of patients received modular neck adapters with neutral or 7.5 degrees retroversion. No 140 degrees neck and no anteverted neck adapters were used. Radiological results of the 2/3 porous coated hip stem showed a metaphyseal bone remodelling with hypertrophies in coated Gruen zones 3 (17%) and 6 (46%) and marked spot welds and increased bone density (86%) in the distal area of the coating. Primary implant migration between 2 and 10 mm was present in 7 cases due to a low osteotomy and implant position combined with an implant undersizing and lack of proximal-lateral support. At the time of the last follow-up these cases had no clinical symptoms with an average HHS of 96 points and with full bony integration.

CONCLUSION

Our results support the use of the investigated short hip stem for THA when the femoral bone quality and morphology support the metaphyseal anchoring concept. The surgical technique must avoid a stem position without proximal-lateral cortical contact to the femoral osteotomy, as this reduces primary implant stability. Further follow-up is necessary to validate the long-term success of this procedure.