Purpose: Extracortical bone bridging and ingrowth have been shown to reduce stresses on the stem and cement mantle of tumor endoprostheses. The purpose of this study was to assess the effect of bone morphogenetic protein 7 (BMP-7) delivered by Peri-Apatiteâ (PA, Stryker Orthopaedics) hydroxyapatite coating on porous segmental replacement prostheses.

Method: Eighteen mature mongrel canines were implanted with unilateral segmental replacement prostheses made of a cobalt-chromium (Co-Cr) alloy and coated with two layers of sintered Co-Cr alloy beads (diameter 600 to 800mm). The control group consisted of a plain porous coated segmental prosthesis without any PA coating. Group 2 consisted of a PA-coated segmental prosthesis coated with buffer solution. Group three consisted of a PA-coated segmental prosthesis loaded with rhBMP-7 (Stryker Biotech) in a buffer solution carrier. Group 1 had the implant only. Group 2 had the buffer solution evenly applied to the porous coat and group 3 had 2.9 mg of BMP-7 in liquid buffer solution evenly applied. The canines were allowed to fully bear weight without restrictions. The femurs were retrieved at twelve weeks for radiographic and histologic analysis.

Results: Gross and radiographic data of the retrieved specimens showed that all six PA-coated implants augmented with BMP-7 had complete bone bridging; only one of the PA-coated implants and only two of the plain porous implants were completely bridged. There was a greater percentage of bone apposition for the BMP-7 augmented PA-coated group compared to both the plain (p=0.0026) and the PA-coated (p=0.0001). There was no difference in bone formation or bone apposition between the plain and PA-coated groups. Histology revealed greater depth of bone ingrowth in the BMP-7 augmented PA-coated group as compared to the plain (p< 0.0001) and the PA-coated (p< 0.0001) groups. There was also significantly greater bone apposition in the BMP-7 augmented PA coated groups as compared to the plain (p=0.0014) and PA-coated (p=0.0067) groups. There was no significant difference in depth of bone ingrowth or bone apposition between the plain and PA-coated groups.

Conclusion: BMP-7 when used to augment PA-coated prostheses in a canine segmental defect model can significantly improve extracortical bone bridging and bone ingrowth. PA-coated implants may be considered to deliver the exogenous biological growth factors.

Purpose: Management of local recurrence (LR) remains unclear. Optimal management of primary tumour by specialised teams minimises this risk. However, previous treatments may impact on the available options when LR is encountered. We thus studied the outcome of this population with recurrent STS.

Method: Retrospective review was carried based on our prospective sarcoma databases. DFSP and ALT were excluded. Among 618 primarily managed STS we found 35 cases of local recurrences (5.7%). Median f-up after LR was 14 mos (0–98).

Results: Twenty were female. Mean age was 54 (Range 15 – 92). 22 involved lower limb, 11 upper limb and 2 the trunk. Mean delay from original surgery was 23 mos (3–75) and the mean size of LR was 4.7 cm (0.4–28.0 cm). Primary tumours were superficial in 4 and deep in 31 while recurrences were found superficial in 8 and deep in 26. Most frequent histology was MFH 8, Leiomyosarcoma 6, Liposarcoma, synovial sarcoma and MPNST had 4 each. 84% were high grade. Only 23 showed no meta-static disease at time LR was diagnosed. All 5 pts without initial RT got RT for their LR. 7 pts with therapeutic level of RT to the primary tumour got full course of RT as well for their LR. 11 did not undergo surgery. 6/18 who had initial RT underwent amputation as opposed to 0/6 who did not. Trend to amputate was for younger age, deep and large tumour and previous RT. Ultimatly, 21(60%) locally recurrent tumours showed metastatic disease; 6 prior diagnosis of LR, 6 concomitantly and 9 after with an average delay of 17 months (1–24). 6 pts developed additional local recurrences.

Conclusion: Although infrequent local recurrence correlates with impaired outcome. Albeit challenging, limb salvage and additional radiotherapy remain possible despite optimal multi modality management of the initial tumour.