Durom™-Hip-Oberflächenersatz am Hüftgelenk: Erste klinische Ergebnisse mit dem lateralen Zugang

Towards the First Generation of Biomimetic Fixation for Resurfacing Arthroplasty Endoprostheses

This paper presents advances in designs of resurfacing arthroplasty endoprostheses that occurred through their historical generations. The critical characteristics of contemporary generation hip resurfacing arthroplasty endoprostheses are given and the failures resulting from the specific generation cemented and short stem fixation of the femoral component are reviewed. On the background of these failures, the critical need arises for an alternative approach to the fixation of components of resurfacing arthroplasty leading towards the first generation of biomimetic fixation for resurfacing arthroplasty endoprostheses. The state of the art of the completed bioengineering research on the first biomimetic fixation for resurfacing arthroplasty endoprostheses is presented. This new design type of completely cementless and stemless resurfacing arthroplasty endoprostheses of the hip joint (and other joints), where endoprosthesis components are embedded in the surrounding bone via the prototype biomimetic multi-spiked connecting scaffold (MSC-Scaffold), initiates the first at all generations of biomimetic endoprostheses of diarthrodial joints.

Early failure of the Durom prosthesis in metal-on-metal hip resurfacing in Chinese patients

Hip resurfacing (HR) is being used increasingly as an alterative to total hip arthroplasty in osteonecrosis (ON) and ankylosing spondylitis (AS) of the hip. We performed 141 consecutive HR arthroplasties in 111 patients comprising 3 etiology groups: ON, AS, and osteoarthritis (OA). After retrospective study of retrieved components, we hypothesized that the main reason for revision was femoral loosening in the ON group (4 of 46 hips; 8.7%) and femoral-neck fracture in the AS group (3 of 58 hips; 5.2%). Necrotic areas were seen on femoral heads retrieved from patients with femoral loosening, whereas femoral heads were fixed tightly to components in patients with femoral-neck fractures. Etiology may be an important risk factor for postoperative complications.

High revision rate at 5 years after hip resurfacing with the Durom implant

BACKGROUND/RATIONALE

There is growing evidence that different resurfacing implants are associated with variable survival and revision rates. A registry analysis indicated the Durom resurfacing implant had high revision rates at 5 years, whereas three original studies reported low revision rates at short-term followups. Thus, the revision rates appear controversial.

QUESTIONS/PURPOSES

We therefore assessed (1) the survivorship including differences between women and men at a mean of 5 years after resurfacing with the Durom implant, and (2) clinical scores and radiographic parameters.

PATIENTS AND METHODS

We prospectively followed all 100 Durom hip resurfacings implanted in 91 patients (25 women and 66 men; mean age, 52 years) between 2003 and 2004. Survivorship analysis was performed with pending revision or revision for any reason as the endpoint. The minimum followup was 47 months (mean, 60 months; range, 47-72 months).

RESULTS

At a mean of 5 years, 11 hips were revised for various reasons. Cumulative survival was 88.2% for all patients and 81.5% for women. The mean Oxford (OHS) and Harris hip (HHS) scores were 14.6 and 94.7, respectively. The mean UCLA activity level was 7.9. Sclerotic changes around the short femoral stem (pedestal sign) were detected in 40% of the hips. We observed considerable femoral neck thinning with component-to-neck ratios of 0.85 preoperatively and 0.82 at 5 years.

CONCLUSIONS

Our study highlights a high revision rate 5 years after hip resurfacing with the Durom implant. This observation underlines previous findings from registry data and suggests that revision rates increase with time.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Causes of early failure in a multicenter clinical trial of hip resurfacing

The purpose of this study was to evaluate the clinical outcomes and possible causes of early failure in a multicenter trial of metal-on-metal hip resurfacing. Two hundred patients were prospectively enrolled and followed for an average of 31.2 months (range, 12-54 months). Of 200 patients, 14 (7.0%) required revision surgery at a mean time of 19.5 months (range, 3-47 months). Patients with failures were significantly younger and heavier than the nonfailures, and all were male. Patients who were revised did not differ from those who were not revised in terms of radiographic outcomes, but they did report lower functional outcome scores at all preoperative and postoperative testing intervals. Most failures (10/14) were related to early acetabular loosening. The learning curve was likely a factor in these cup failures. This report highlights the importance of patient selection and surgical technique in hip resurfacing arthroplasty. It is anticipated that further surgical experience will lead to a reduction in this high early failure rate.

[Fluoroscopic navigation versus conventional manual positioning of the femoral component for hip resurfacing: first experimental trial]

BACKGROUND

The most essential improvement of modern hip resurfacing arthroplasty is the metal-on-metal bearing as well as the integration of a procedure for the exact and repeatable positioning of the femoral component through a specific mechanical alignment instrument. Nevertheless, the main reasons for early implant failure are mal-positioning of the femoral component and notching of the femoral neck during femoral head preparation.

MATERIALS AND METHODS

In the context of an in vitro study, in each case six DUROM-Hip resurfacing prostheses were implanted in artificial femora with the prosthesis-specific mechanical alignment instrument, as well as under navigation control. The aim of the study was to evaluate the functionality and accuracy of a computer-assisted planning and navigation system on the basis of a navigation module library from Surgitaix AG (Aachen, Germany), as well as a comparison with the prosthesis-specific mechanical alignment instrument.

RESULTS

The main angulation error between planning and navigation of the stem-shaft angle was 0.2+/-1.2 degrees for the navigation system and 6.5+/-4.1 degrees for the mechanical alignment instrument, the main anterior offset error was 1.2+/-1.2 mm vs. -0.83+/-4.1 mm. The mean time for all five planning and navigation steps was 17+/-1.2 min vs. 14+/-0.8 min. The main distance error between planning and navigation was 1.9+/-0.6 mm for the navigation system, and 5.3+/-2.4 mm for the mechanical alignment instrument. Femoral notching was not observed for navigational or conventional positioning.

CONCLUSION

The computer-assisted fluoroscopic planning and navigation system for hip resurfacing showed, within the scope of this in vitro study, first promising experiences. The system approves a practicable planning with a high accuracy in implementation. Nevertheless, the potential benefit has to be evaluated in further clinical studies, especially from the perspective of a possible integration of this navigation system into the clinical workflow. Further studies should consider a fluoroscopy-assisted range of motion assessment under consideration of an additional cup-module to enhance the postoperative range of motion after hip resurfacing procedures.