Abstract
Background
The Kotz Modular Femoral Tibial Replacement system has been one of the most widely utilised uncemented modular systems for bone and joint reconstruction after tumour resection. We have identified a significant incidence of mechanical failure and breakage of the prosthesis. The purpose of this investigation is to review the modes of implant failure and the outcomes after prosthetic revision for a broken Kotz prosthesis.
Methods
Over 20 years there were 121 distal femoral, 55 proximal tibial, 47 proximal femoral and 12 total femoral replacements performed.
Results
Out of 180 currently living patients there were 27 implant fractures in 23 patients (13%) with 22 distal femoral and five proximal tibial implant failures. Mechanical failures occurred at a mean of 77 months (range 24-170). There were 21 stem fractures. Five fractured at the derotation lug and one fractured the tibial housing. Lug fracture is an unreported mode of failure of these implants. The implant design selected for revision was very much dependent on when the fractured implant was revised. Eleven patients had new KMFTR stems inserted; 4 Restoration stems (one of which was cemented), 3 GMRS stems (one of which was cemented), two total femora and one Compress (Biomet) implants have been utilised, all with custom adaptors between the stem and the KMFTR system. There were 12 complications (44%), seven infections, three implant re-fractures, one vascular insufficiency necessitating amputation and one per-prosthetic fracture. The mean pre-implant fracture and post-revision TESS scores were 80.9 (Range 54.2-98.3) and 79.1 (50-96.7). The MSTS87 pre- and post- scores were 26.8 (14-33) and 26.1 (15-33) respectively. The MSTS93 also demonstrated no differences in the pre-fracture and post-revision scores with 75.4 (50-93) and 74.8 (40-100).
Conclusion
Our data illustrate that these prostheses can often be successfully revised by trephining out the broken stem and inserting new uncemented stems. Functional outcome continues to be good and is comparable to pre-revision levels, despite a 44% complication rate.
