Original Article
Bioabsorbable magnesium versus standard titanium compression screws for fixation of distal metatarsal osteotomies – 3 year results of a randomized clinical trial

https://doi.org/10.1016/j.jos.2017.11.005Get rights and content

Abstract

Background

For the treatment of hallux valgus commonly distal metatarsal osteotomies are performed. Persistent problems due to the hardware and the necessity of hardware removal has led to the development of absorbable implants. To overcome the limitations of formerly used materials for biodegradable implants, recently magnesium has been introduced as a novel implant material. This is the first study showing mid-term clinical and radiological (MRI) data after using magnesium implants for fixation of distal metatarsal osteotomies.

Material and methods

26 patients with symptomatic hallux valgus were included in the study. They were randomly selected to be treated with a magnesium or standard titanium screw for fixation of a modified distal metatarsal osteotomy. The patients had a standardized clinical follow up and MRI investigation 3 years' post-surgery. The clinical tests included the range of motion of the MTP 1, the AOFAS, FAAM and SF-36 scores. Further on the pain was evaluated on a VAS.

Results

Eight patients of the magnesium group and 6 of the titanium group had a full clinical and MRI follow up 3 years postoperatively. One patient was lost to follow-up. All other patients could be interviewed, but denied full study participation. There was a significant improvement for all tested clinical scores (AOFAS, SF-36, FAAM, Pain-NRS) from pre-to postoperative investigation, but no statistically relevant difference between the groups. Magnesium implants showed significantly less artifacts in the MRI, no implant related cysts were found and the implant was under degradation three years postoperatively.

Conclusion

In this study, bioabsorbable magnesium implants showed comparable clinical results to titanium standard implants 3 years after distal modified metatarsal osteotomy and were more suitable for radiologic analysis.

Level of evidence

2.

Section snippets

Background

For hallux valgus deformities, commonly distal metatarsal osteotomies (DMO) are performed. The chevron osteotomy was initially described for mild to moderate deformities by Corless and later Austin [1]. Generally good clinical results are achieved with this operation [2], [3]. Although initially internal fixation was not considered necessary, for better control of the osteotomy and to prevent tilting of the metatarsal head, fixation is nowadays generally recommended. Different fixation

Study design

Between March 2010 and July 2011, we recruited the patients for this randomized controlled study. Inclusion criteria were defined as symptomatic hallux valgus with indication for chevron osteotomy and no additional surgery, age between 40 and 79 years, secure contraceptive method in female patients and no other pathology of the lower extremity. Exclusion criteria were set as previous operations on the symptomatic foot, BMI >32, pregnancy, neurological pathologies, bone mineral density

Clinical results

There was no preoperative difference between the Mgsingle bond and the Ti-group regarding AOFAS (p = 0.874) and pain-NRS (p = 0.295). The AOFAS (p = 0.002) and pain-NRS (p = 0.001) improved significantly from pre-to 3 years postoperatively. Postoperatively there were no significant differences for pain-NRS (p = 0.94), AOFAS (p = 0.285), FAAM-ADL (p = 0.756), FAAM-Sport (p = 0.606) and SF-36 (p = 0.38) between the Mg and the Ti-groups (Table 2).

All patients achieved the preoperative activity level. The

Discussion

In this mid-term follow-up study, we found comparable clinical results after fixation of distal metatarsal osteotomies using metallic bioabsorbable Mg-screws or standard Ti-screws. MRI after 3 years showed a sufficient bone healing and less artifacts in the Mg-group compared to the standard treatment group. In the position of the former implant a hypointense structure was found indicating a mineralized structure most probably similar to cortical bone.

Conclusion

In this study, distal metatarsal osteotomies fixed with either a magnesium or titanium implant show no significant difference in the clinical outcome after three years. Magnesium implants have advantages in imaging due to less artifacts. Magnesium based implants are degraded but are not fully remodeled after 3 years, yet.

Compliance with ethical standards

Conflict of Interest: The study was financially supported by Syntellix AG, Hannover, Germany. HW was member of the supervisory board of Syntellix AG, Hannover, Germany.

Ethical approval: The study was approved by the responsible ethical board and registered in the German clinical trial register.

Informed consent: Informed consent was obtained from all individual participants included in the study.

Acknowledgement

We thank Yvonne Noll for the organization of the follow up controls and data acquisition. We thank Christian Modrejewski for patient examination and data collection.

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  • Cited by (0)

    The work was performed at the: Orthopedic Clinic in Diakovere Annastift, Hannover Medical School, Anna-von-Borries Strasse 1-7, 30625 Hannover, Germany.

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