How Can We Differentiate Local Recurrence From Heterotopic Ossification After Resection and Implantation of an Oncologic Knee Prosthesis in Patients with a Bone Sarcoma?

BACKGROUND: Heterotopic ossification (HO) is common after total joint arthroplasty and usually does not cause diagnostic problems. However, the occurrence of HO after oncologic prostheses implantation can be troublesome as it may mimic a locally recurrent tumor. Because this distinction could have a profound impact on the surgeon and patient, it is important to distinguish the two entities; to our knowledge, no study has evaluated this after oncologic endoprosthetic reconstruction around the knee after tumor resection. QUESTIONS/PURPOSES: (1) How common is the occurrence of HO compared with local recurrence (LR) after resection of bone sarcoma and the use of an oncologic knee prosthesis? (2) Are there any factors associated with the development of HO after limb salvage procedures with an endoprosthesis? (3) What features allow the surgeon to differentiate HO from a locally recurrent tumor in this setting? METHODS: Between 2002 and 2018, we performed 409 resections of primary bone tumors followed by reconstructions with oncologic endoprostheses. Of these, 17% (71 of 409) died before 2 years and did not have HO at that time, 2% (8 of 409) were lost to follow-up before 2 years, and another 2% (10 of 409) did not have radiographs available at a minimum of 2 years after surgery (and had not developed HO before then), and so could not be analyzed, leaving 320 patients for analysis in this retrospective study. Forty-two patients were excluded; 2% (5 of 320) for a history of failed allograft reconstruction, 3% (8 of 320) for pathologic fracture at presentation, 2% (6 of 320) for inadequate or complicated biopsy, 1% (2 of 320) for stem fractures, 2% (7 of 320) for stem loosening, and 4% (14 of 320) for extracortical bone bridging, leaving 278 patients for final evaluation. Two observers analyzed AP and lateral radiographs for signs of HO at a mean follow-up of 63 ± 33 months after surgery. We defined HO as extraskeletal bone formation in soft tissues. The primary study endpoint was survivorship free from HO, as ascertained by a competing-risks estimator. To identify factors associated with HO appearance, the demographic, radiographic, clinical, pathologic, and surgical characteristics were compared between patients with HO and those who had no lesion. Characteristic features were also compared between patients with HO and those with LR to help their differentiation. Univariate analysis was used for all statistical evaluations. RESULTS: HO developed in 8% (21 of 278) of patients in whom oncologic knee prosthesis was implanted. LR developed in 10% (28 of 278) of the patients. According to survivorship estimates, the HO-free survival rate was not different from the LR-free survival rate at 2 years after oncologic knee reconstruction (76 ± 5% [95% CI 63 to 87] versus 74 ± 5% [95% CI 62 to 88]; p = 0.19). History of infection was more common in patients with HO than in patients with no lesion (19% [4 of 21] versus 5% [12 of 229], Odds ratio [OR] 6 [95% CI 2 to 17]; p < 0.001). The male sex was more common in the HO group as well (76% [16 of 21] versus 55% [128 of 229], OR 2 [95% CI 1 to 5]; p = 0.03). The Modular Universal Tumor and Revision System prosthesis was more frequently used in patients with HO (67% [14 of 21]) compared to those with no lesions (40% [92 of 229]; OR 2 [95% CI 1 to 5]; p = 0.02). The lesion border in radiographs was ill-defined in 19% (4 of 21) of patients with HO and 100% (28 of 28) of patients with LR (OR 8 [95% CI 3 to 20]; p < 0.001). The median time to the appearance of HO was shorter than the time to LR (8 months [3 to 13] versus 16 months [11 to 21], [95% CI 10 to 13]; p < 0.001). Pain at presentation was more frequent in patients with LR than in those with HO (86% [24 of 28] versus 14% [3 of 21], OR 36 [95% CI 7 to 181]; p < 0.001). CONCLUSION: HO may occur after the use of oncologic knee prostheses for reconstruction after tumor resection. In most patients, HO could be differentiated from local recurrence through identifying a well-defined border on radiographs. Otherwise, factors such as an earlier time of presentation and absence of pain could suggest an HO, rather than an LR. LEVEL OF EVIDENCE: Level III, therapeutic study.

Comparison of characteristic features and local recurrence in syndromic versus non-syndromic multifocal non-ossifying fibroma.

BACKGROUND: Multiple non-ossifying fibromas (MNOF) could be presented with other extraskeletal anomalies (syndromic) or not (non-syndromic). In this study, we aimed to compare characteristic features and local recurrence between symptomatic syndromic and non-syndromic MNOFs. METHODS: Thirty-five patients with symptomatic MNOF were included in this study, comprised of 30 patients without the café-au-lait spot (non-syndromic) and five with café-au-lait spots plus other signs of neurofibromatosis type 1 (syndromic). Characteristic features of the patients and lesions were compared between syndromic and non-syndromic MNOFs. The lesions were treated with curettage and bone graft. The rate of local recurrences was also compared between the two groups of syndromic and non-syndromic MNOF. RESULTS: Study population included 19 (54.3%) males and 16 (45.7%) females with the mean age of 7.63 ± 3.1 years (range 4-11). The mean follow-up of the patients was 65.6 ± 38.2 months (range 24-96). The lesion was bilateral in 13.3% of non-syndromic MNOFs and 80% of syndromic MNOFs. This difference was statistically significant (p = 0.01). After curettage and bone grafting, the lesion recurred in 6.7%of non-syndromic MNOFs and 60% of the syndromic MNOF. This difference was statistically significant, as well (p = 0.01). No other significant difference was found between syndromic and non-syndromic MNOFs. CONCLUSIONS: The syndromic form of MNOF is much less prevalent and is associated with a higher rate of recurrence after surgical removal. Therefore, a more rigorous removal of the MNOF lesions might be necessary when presented in a syndromic context.

Extended curettage versus en bloc resection for the treatment of grade 3 giant cell tumour of the knee with pathologic fracture: a retrospective study.

PURPOSE: For the treatment of giant cell tumour of the bone (GCTB) around the knee, preserving the native joint confers advantages over scarifying it. But, there is a controversy about the efficacy of intralesional curettage versus en bloc resection for treatment of such lesions. In this study, we compared local recurrence, functional outcomes, and complications of extended curettage and en bloc resection in these lesions. METHODS: Patients with grade 3 GCTB of the distal femur or proximal tibia who were presented with a pathologic fracture and treated with either en bloc resection (n = 22) or extended curettage (n = 20) were included. The mean follow-up of the patients was 6.4 ± 1.9 years in the resection group and 5.5 ± 2.4 years in the extended curettage group. The primary outcome was a local recurrence. Secondary outcomes were limb function evaluated by the Musculoskeletal Tumor Society (MSTS) score and rate of complications. RESULTS: Local recurrence was seen in four (20%) patients of the curettage group and three (13.7%) patients of the resection group (P = 0.69). The mean MSTS score was 24 ± 1.9 in the resection group and 26.5 ± 1.3 in the curettage group (P < 0.001). The number of complications was not significantly different between the two study groups (P = 0.49). However, the number of complications that required revision surgery was significantly more in the resection group (P = 0.049). CONCLUSION: In grade 3 GCTB around the knee with pathologic fracture, extended curettage results in comparable oncologic outcomes to en bloc resection, while providing better function and a lower rate of revision.