gms | German Medical Science

Objectives: In a four-year follow-up comparative study we are presenting clinical and radiological outcomes of an implantation of two cementless short femoral stems: MINIHIP (Corin) and SMF (Smith&Nephew). Both are uncemented titanium stems shorter than conventional stems and can be implanted through a minimal invasive approach. In Feyen's and Shimmin's Classification MINIHIP stem it is classified as Partial Collum with neck preserving osteotomy and SMF as Trocanter harming. Short-stem total hip arthroplasty should be a bone-conserving procedure and an alternative for the younger and more active patients.

Methods: We have analized the data from a 130 patients (55F,75M), the mean age was 57 years (range 31-82Y). 59 left and 71 right hips were operated on. Causes for operative treatment were 83 (64%) primary coxarthrosis, 31 (24%)avascular necrosis of the femoral haed and 16(12%) secondary coxarthrosis. 129 patients (97.4%) were operated on with a a minimal invasive anterior approach (DAA), 1 with (0.7%) postero-lateral. The functional outcomes were analyzed on the basis of Harris Hip and WOMAC scores.

Results: The evaluation of the radiographic outcomes were assessed for:

• malalignment: SMF 7 cases (8%) and MINIHIP 1(2%)
• rotational stem migration: SMF 67 cases (79.7%), MINIHIP: 11(24%) /P=0.0009->extremely statistically significant (Figure 1 [Fig. 1], Case 1)
• vertical stem migration SMF: 65 cases (77%), MINIHIP: 15 (33%) /P=0.0338->statistically significant (Figure 1 [Fig. 1], Case 2)
• proximal femur neck osteolysis: SMF 4 cases (5%), MINIHIP: 0 (0% )
• distal femur cortical hypertrophy: SMF 33 cases (39%), MINIHIP: 5 (11%)

Complications included:

• intraoperative periprosthetic fractures:SMF 4 cases (7%), MINIHIP: 4 (5%)
• superficial infection: SMF 2 cases (2%), MINIHIP: 1 (2%)
• incidences of thigh pain: SMF 9 cases (11%) and MINIHIP: 1 (2%)
• lateral femoral cutaneous nerve injury (neuropraxia, axonotmesis, neurotmesis): SMF 11 cases (18%), MINIHIP: 5 (11%)

Revision hip arthroplasty rate was 7.1% (6 cases) for SMF stem and 0% MINIHIP.

The average Harris Hip Score at last the follow-up was 91.8 (range 73-100).

The average WOMAC score was 88,9 (range 64.1-98.4).

Conclusions:

• Both of the stems can be implanted using a minimal invasive approach
• Both of the stems can be replaced with the conventional hip implant if a revision hip arthroplasty is necessary.
• At the 4-year follow-up survivorship was 92.8% for SMF and 100% for MINIHIP
• There are significant statistical differences in the radiological results, especially in the vertical (P=0.0338) and the rotational (P=0.0009) angular stem stability
• By reason of a high rate of vertical and rotational angular stem migration we decided to stop the implantation of SMF stem.