Purpose of this paper was to review the Rizzoli experience in prosthetic reconstruction of the knee after resection of bone tumors with special attention to major complications and functional outcome.

Material: 669 knee modular uncemented prostheses were implanted between 1983 and 2006 after resection of the distal femur, total femur or proximal tibia. These prostheses include 126 first generation Kotz prosthesis (KMFTR) and 543 second generation HMRS prostheses.

Methods: All patients are followed periodically in the clinic. Data for this study was obtained from clinical charts; imaging studies were reviewed with special attention to prosthesis related major complications requiring revision surgery. Revision for polyethylene wear was considered a minor complications, since it does not imply change of main prosthetic components, thus failure of the implant. Functional results were assessed according to the MSTS system.

Since abrupt data could be misleading due to the oncologic population and related deaths (although 2/3 of the patients were cured or long survivors), to censore the implant unrelated events a statistical analysis of the implant survival was performed and Kaplan-Meyer curves of implant survival were studied.

Results: In the 126 KMFTR group major complications included infection 13%, breakage of the stems 12%, aseptic loosening 8.7%, while revision for polyethylene wear rated 45%.

In 543 HMRS prostheses major complications were infection 8%, stem breakage 2%, aseptic loosening 4%, while revision for polyethylene wear components rated 7.4%.

Techniques of revisions were analyzed, as well as the outcome of revised cases, which showed that about 2/3 of the patients treated for major complications do well, although the risk for further complications is significantly incresed in revised implants.

Functional results were evaluated according to the MSTS system: in KMFTR prostheses were good or excellent in 80% of the patients, while in HMRS were good or excellent in 90% of the patients.

Discussion: The reduction of major complication rate with the newer designs of the modular prosthesis was statistically significant and this seems to confirm that newer materials and a modified stem design positively affected the implant survival. Also the wear of polyethylene component was dramatically decreased in the newer prosthetic design. Functional results were satisfactory in most of the patients that did not experience major complications, with a trend to improvement in the newer design. Revision surgery is technically demanding and sometimes newer ‘hybrid’ techniques are suggested, implying the use of bone allografts.

Appropriate timing of revisions is crucial. An early treatment of complications can improve the final outcome.

Purpose of this study is to report the preliminary results of the clinical experience of the Rizzoli with a new modular reconstructive tumor prosthesis for the lower limb (GMRS-Stryker).

Material and methods: based on the clinical experience and the review of 842 cases of modular tumor prosthesis for the lower limb, a new prosthetic design was introduced derived from the previous. It is a modular system with a rotating hinge mechanism for the knee and several possible options for the stems, including titanium and chromium-cobalt-molybdenum stems, cemented and uncemented, curved and straight-fluted, with or without hydroxyapatite coating. Moreover adaptors were available to revise older HMRS implants with GMRS components.

Between October 2003 and march 2006 this system was implanted at the Rizzoli in 85 cases. This series included 42 males and 43 females, ranging in age from 8 to 76 years. The sites of prosthetic reconstruction were distal femur in 60 cases, proximal femur in 7, total femur in 1, proximal tibia in 17 cases.

There were 79 oncologic and 6 non oncologic diagnoses. The histological diagnoses of the oncologic cases included 11 giant cell tumors and 68 malignant tumor: 52 osteosarcomas, 7 spindle cells sarcomas, 6 Ewing’s sarcoma, 3 chondrosarcomas. Of the 79 oncologic cases 55 were primary reconstructions with GMRS prosthesis and 24 secondary reconstructions for failure of a previous reconstruction.

In 16 cases HMRS/GMRS hybrid implants were used in reconstruction or revision, using adaptors.

All patients are periodically checked in the outpatient clinic of the Rizzoli.

Complications were reported and analyzed, x-rays were reviewed and pertinent information achieved for each patient. Functional results were assessed according to the MSTS system.

Results: at a short follow up (min 5 months, max 30 months) showed 76 patients NED (11 benign and 65 malignant), 1 NED1 after treatment of local recurrence, 4 NED1 after treatment of metastases.

There was 1 case of infection, treated with removal of the implant and spacer with antibiotics. There were 3 disruptions of the knee extensor apparatus, 1 patellar instability treated by revision of the prosthesis.

Functional result were evaluable in 59 cases and showed a function of 26% to 50% in 14% of pts, of 51% to 75% in 19%, over 76% in 67%. Results were considered good or excellent in 86% of the evaluated patients.

Conclusions: Although the results have been evaluated at a short term follow up, this prosthetic system is promising and it can also be used in some non oncological settings, such as challenging revisions of prosthetic failures with massive bone loss or some post-radiation non unions or allografts failures.