Carbon fibre reinforced PEEK versus conventional prophylactic internal fixation in patients with low grade chondrosarcoma

Chondrosarcoma accounts for 25% of the primairy bone sarcomas. The clinical
behaviour of these tumours is highly variable and unpredictable. Grade 2 and 3
are considered highly aggressive and invasive sarcomas, while Grade 1 is often
considered to be slowly growing and not prone to metastasize.

The 5-year survival rates reported for low-grade chodrosarcomas are 85%-90% in
contrast to 20-40% reported survival rates for high grade tumours.
Because of the relative ineffectiveness of chemo- and radiotherapy, surgical
excision is the treatment of choice3.

For grade 2 and 3 chondrosarcomas, wide excision is universally accepted as
standard care. For grade 1 chondorsarcomas, treatment is subject of debate.

Local treatment with intralesional curettage and an adjuvant therapy showed
equivalent results to en bloc resection with respect to survival, recurrence
and metastasizing potential11. En bloc resection and subsequent reconstruction
with endoprostheses, bonegrafting or combinations of the before mentioned puts
patients at risk for complications such as infection, aseptic loosening,
periprosthetic fracturing and nonunion.

Local treatment is composed of intralesional curettage with phenolisation or
cryotherapy as adjuvant therapy. After curettage and adjuvant therapy, the
defect is filled with auto- or allogenic bone grafts with or without PMMA.
Stability of the construct is assessed and decision is made if internal
fixation is needed to prevent secondary pathologic fractures.

Recurrence rates after curettage and adjuvant therapy are 0-13.3%. Therefore
accurate radiographic surveillance is of the upmost importance. Metallic
implants impede reliable follow up by creating field inhomogeneity and scatter
artifacts on MRI and CT and by interference on x-ray18. Despite of the fact
that secondary pathologic fracture rates are 10 up to 17% in literature some
studies advocate that internal fixation should be avoided because of
aforementioned scatter and interference5. If field inhomogeneity and scatter on
imaging would no longer be an issue internal fixation could be indicated more
often and could reduce secondary pathologic fracture risk.

Because of the potential imaging advantages at follow up and the subsequent
potential to reduce secondary pathologic fractures in ACT/chondrosarcoma grade
1 cases, we will perform a prospective cohort study to test radiographic
properties of CFR-PEEK distal femoral plate osteosynthesis. Data will be
compared to a retrospective cohort with conventional titanium distal femoral
plate osteosynthesis. Visualisation of the excochleation borders and cortical
window will be scored. Volumes of field inhomogeneity and scatter artifacts
will be measured and ingrowth of the cortical window will be assessed.

Objective is to compare field inhomogeinity between conventional titanium
osteosynthesis and CFR-PEEK osteosynthesis on MR imaging. Visualisation of
regions of interest will be scored and volume of field inhomogeneity will be
calculated.

This is a prospective cohort study to evaluate radiographic properties of the
CFR-PEEK distal femoral internal fixation plates. Field inhomogeneity on MR
imaging in patients that underwent curettage and adjuvant therapy for an
ACT/grade 1 chondrosarcoma will be analysed. Follow-up will be one year.
In addition, a retrospective study will be performed to compare results with
the prospectively collected results of the CFR-PEEK distal femoral internal
fixation plates. Data will be collected prospectively according to the standard
follow up protocol.

Distal femoral prophylactic plate osteosynthesis with a Carbon Fibre Reinforced
PolyEtherEtherKetone distal femoral plate (CFR-PEEK, Carbofix).

Potential benefit of enrollment in this study is superior radiographic
surveillance due to the absence of field inhomogeneity and scatter artifacts
caused by titanium implants. Recurrences could be detected in an earlier stage
which may have a positive effect on limb salvage and oncologic outcome.
Furthermore the field inhomogeneity and scatter artifacts in titanium implants
have been causing a restraint on the use of prophylactic osteosynthesis. Using
CFR-PEEK implants could widen indication of prophylactic use of osteosynthesis
and thus could reduce secondary fracture rates after curettage and adjuvant
therapy.
Mechanical properties of the CFR-PEEK implants (i.e. higher bending strength
and improved modulus of elasticity) could reduce hardware failure rates and
fixation failure rates.

Potential risk of using CFR-PEEK is brittleness of the CFR-PEEK implants when
hardware failure occurs. In literature, only in the early generation CFR-PEEK
implants this complication was seen. Improved manufacturing processes and
thicker composites and coatings resulted in diminished failure rates. Although
biocompatibility is addressed in literature, one case report reported a
biologic reaction to carbon particles. Therefore, tissue reactions should be
considered a potential risk.

All follow-up will be part of normal patient care, no extra imaging or
questionnaires will be used outside standard care.