Cemented endoprosthetic reconstruction of the proximal tibia: how long do they last?

Abstract

Background: The few available studies documenting the long-term survival of cemented proximal tibial endoprostheses for musculoskeletal tumors do not differentiate between stem designs or patient diagnosis. There is wide variation in survival rates reported, possibly a result of this heterogeneity in patient population and implant design.

Questions/purposes: We therefore asked: (1) How long do proximal tibial endoprostheses last? (2) What is the typical long-term functional result after proximal tibial replacement? And (3) what are the short- and long-term complications associated with endoprosthetic reconstruction of the proximal tibia, particularly with respect to the soft tissue reconstruction?

Patients and methods: We retrospectively reviewed 52 patients with 52 proximal tibial endoprosthetic reconstructions for a tumor-related diagnosis. Kaplan-Meier survivorship analysis was performed using revision of the stemmed components for any reason as an endpoint for implants, and death due to disease progression for patients. Function was assessed using the MSTS scoring system. The minimum followup was 1 month (mean, 96 months: range, 1-284 months; median, 69 months).

Results: Using revision of the stemmed components for any reason as an end point, overall prosthesis survival at 5, 10, 15, and 20 years was 94%, 86%, 66%, and 37%, respectively. The 29 modular implants demonstrated a trend toward improved survival compared to the 23 custom-designed components, with a 15-year survivorship of 88% versus 63%. The mean postoperative Musculoskeletal Tumor Society score at most recent followup was 82% of normal function (mean raw score, 24.6; range, 4-29).

Conclusions: Cemented endoprosthetic reconstruction of the proximal tibia provides a reliable method of reconstruction following tumor resection.

Fig. 1

Kaplan-Meier survivorship analysis shows overall prosthesis survival (n = 52). Using revision of the stemmed components for any reason as an end point, overall prosthesis survival at 5, 10, 15, and 20 years was 93.8%, 86.4%, 65.8%, and 37.0%, respectively. Dashed lines represent 95% confidence intervals.

Fig. 2A–B

Kaplan-Meier survivorship analysis shows (A) modular (n = 29) versus (B) custom (n = 23) implant survival. Although not statistically significant, the 29 modular implants demonstrated a trend toward improved survival compared to the 23 custom-designed components, with a 15-year survivorship of 87.5% versus 62.9% (p = 0.13). Dashed lines represent 95% confidence intervals.

Fig. 3A–E

Images illustrate the case of a patient experiencing aseptic loosening of a tibial stem 20 years after initial procedure. (A) A plain AP radiograph demonstrates the aseptic loosening of the tibial stem. (B) An intraoperative photograph shows revision of the stem. Clinical photographs show the patient’s function at the time of most recent followup, illustrating active range of motion from (C) full extension to (D) 110 degrees of flexion. (E) A plain AP radiograph 2 years following revision showing a well-fixed tibial stem.

Fig. 4A–B

(A) The initial implant design used for the first 10 cases in this series featured extensive extramedullary porous coating with the aim of encouraging bone ingrowth. The coating was removed after bone ingrowth did not occur. The subsequent 10 cases were manufactured without this surface and were noted to demonstrate increased radiographic radiolucent lines and osteolysis. Three of the 10 implants (30%) without this surface demonstrated aseptic loosening, while only three of 42 implants (7.1%) with extramedullary coating showed signs of loosening. (B) An intraoperative photograph at the time of implant revision demonstrates soft tissue ingrowth into the extramedullary porous surface. This ingrowth is thought to provide a barrier that functions to limit access of wear debris to the bone-cement interface.

Fig. 5

A graph shows implant versus patient survival for the entire study cohort. Modular implants performed better than custom implants, with a 15-year survival of 93.7% versus 51.7%, respectively. Patients with low-grade or benign disease and long-term survivors with high-grade localized disease should expect to undergo at least one revision procedure in their lifetime.