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Survival of modern knee tumor megaprostheses: failures, functional results, and a
comparative statistical analysis
#MMPMID24874116
Pala E
; Trovarelli G
; Calabṛ T
; Angelini A
; Abati CN
; Ruggieri P
Clin Orthop Relat Res
2015[Mar]; 473
(3
): 891-9
PMID24874116
show ga
BACKGROUND: Modular megaprostheses are now the most common method of
reconstruction after segmental resection of the long bones in the lower
extremities. Previous studies reported variable outcome and failure rates after
knee megaprosthetic reconstructions. QUESTIONS/PURPOSES: The objectives of this
study were to analyze the results of a modular tumor prosthesis after resection
of bone tumor around the knee with respect to (1) survivorship; (2) failure rate;
(3) comparative survivorship against different sites of reconstructions and of
primary and revision implants; and (4) functional results on the Musculoskeletal
Tumor Society (MSTS) scoring system. METHODS: Between 2003 and 2010, 247
rotating-hinge Global Modular Reconstruction System (GMRS) knee prostheses were
implanted in our institute for malignant and aggressive benign tumors. During
this time, that group represented 23% of the patients who had oncologic
megaprosthesis reconstruction about the knee after resection of primary or
metastatic bone tumors (247 of 1086 patients). In the other 77% of cases we used
other types of oncologic prostheses. Before 2003 we used the older Howmedica
Modular Resection System and Kotz Modular Femur/Tibia Replacement from 2003 we
used mostly the GMRS but we continued to use the HMRS in some cases such as
patients with poor prognoses, elderly patients, or metastatic patients. Sites
included 187 distal femurs and 60 proximal tibias. Causes of megaprosthesis
failure were classified according to Henderson et al. in five types: Type 1 (soft
tissue failure), Type 2 (aseptic loosening), Type 3 (structural failure), Type 4
(infection), and Type 5 (tumor progression). Followup was at a minimum oncologic
followup of 2 years (mean, 4 years; range, 2-8 years). Kaplan-Meier actuarial
curves of implant survival to major failures were done. Functional results were
analyzed according to the MSTS II system; 223 of the 247 were available for
functional scoring (81%). RESULTS: At latest followup, among 175 treated patients
for primary reconstruction, 117 are continuously disease-free, 26 have no
evidence of disease after treatment of relapse, eight are alive with disease, and
24 died from disease. The overall failure rate of the megaprostheses in our
series was 29.1% (72 of 247). Type 1 failure occurred in 8.5% (21 of 247) cases,
Type 2 in 5.6% (14 of 247), Type 3 in 0%, Type 4 in 9.3% (23 of 247), and Type 5
in 5.6% (14 of 247). Kaplan-Meier curve showed an overall implant survival rate
for all types of failures of 70% at 4 years and 58% at 8 years. Prosthetic
survivorship for revisions was 80% at 5 years and for primary reconstructions was
60% at 5 years (p = 0.013). Survivorship to infection was 95% at 5 years for
revision patients and 84% at 5 years for primary patients (p = 0.475). The mean
MSTS score was 84 (25.2; range, 8-30) with no difference between sites of
localization (24.7 in proximal tibia versus 25.4 in distal femur reconstruction;
p = 0.306). CONCLUSIONS: Results at a minimum of 2 years with this modular
prosthesis are satisfactory in terms of survivorship (both oncologic and
reconstructive) and causes and rates of failure. Although these results seem
comparable with other like implants, we will continue to follow this cohort, and
we believe that comparative trials among the available megaprosthesis designs are
called for. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for
Authors for a complete description of levels of evidence.
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