J Korean Orthop Assoc.  2017 Oct;52(5):435-441. 10.4055/jkoa.2017.52.5.435.

Locking Mechanism Failure after Distal Femoral Reconstruction with Modular Universal Tumor and Revision System (MUTARS) Tumor Prosthesis

• Cho WH
• Jeon DG
• Kong CB
• Lee HS
• Song WS

• KMID: 2393516
• DOI: http://doi.org/10.4055/jkoa.2017.52.5.435

Abstract

PURPOSE
We have used Modular Universal Tumor and Revision System (MUTARS) tumor prosthesis to reconstruct segmental resection defect of the distal femur. The purpose of this study was to evaluate the incidence and pattern of locking mechanism breakage and its correlation with other clinical variables.
MATERIALS AND METHODS
We retrospectively reviewed 94 patients who were followed-up for more than one year after tumor prosthesis replacement (MUTARS) between 2008 and 2013. We examined the incidence and timing of locking mechanism (PEEK-OPTIMA) failure. We also evaluated the clinical characteristics of patients experiencing locking mechanism failure and compared them with those of other patients.
RESULTS
At a mean follow-up of 55 months, we observed locking mechanism failure in 10 of 94 patients (10.6%). The mean age of patients with locking mechanism failure was 29 years (range, 13-54 years); the mean weight and height were 169 cm (range, 151-181 cm) and 67 kg (range, 53-89 kg), respectively. The mean body mass index was 23.5 kg/m² (range, 20.5-29.4 kg/m²). The median time interval between replacement and locking mechanism failure was 26.5 months (range, 12-72 months). The mean body weight of patients with failure was higher than that of patients without failure (p=0.019).
CONCLUSION
The incidence of locking mechanism (PEEK-OPTIMA) failure after distal femoral reconstruction with MUTARS was 11%, and there was a correlation between failure and body weight of patients. Advancements in the design and material of locking mechanisms are warranted to reduce the complication.

Keyword

distal femur; tumor prosthesis; MUTARS; locking mechanism

MeSH Terms

Body Mass Index
Body Weight
Femur
Follow-Up Studies
Humans
Incidence
Prostheses and Implants*
Retrospective Studies

Figure

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  Figure 1 Preoperative radiograph of locking mechanism failure after distal femoral reconstruction (case 1). There is no definite signs of loosening around the femoral stem, but there is a radioopaque line (arrow) by the medial aspect of the femoral component, indicating breakage of the locking mechanism.

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  Figure 2 (A) Photograph of the retrieved locking mechanism (PEEK-OPTIMA) shows a breakage at the slot for knee motion, perpendicular to the long axis of the PEEK. (B) Radiography of the intact PEEK shows a radioopaque line on the right side.

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