Allograft augmented with intramedullary cement after resection of a diaphyseal tumour
Surgeons in Mount Sinai Hospital, Toronto (Canada) have reported their own experience of augmented plate reconstruction with allograft following resection of diaphyseal tumours.1 The technique in question involves the use of intercalary allograft and subsequent cement augmentation to create a cement plate fixation construct following tumour excision. This offers a flexible alternative to a megaprosthesis in the limb salvage situation. Although a well recognised technique, there are few long-term studies reporting survival or functional outcomes, and we were delighted here at 360 to read this report of nearly 50 patients, all managed using this technique. This study team reports a prospective cohort series of 46 patients with intercalary allografts augmented with intramedullary cement and fixed using compression plating. Outcomes were evaluated for long-term functional status using the Musculoskeletal Tumor Society (MSTS) scoring system and the Toronto Extremity Salvage Score (TESS). The most common diagnoses were osteosarcoma (n = 16) and chondrosarcoma (n = 9), with the usual pattern of tumour location (femur in 21, the tibia in 16 and the humerus in nine). At a median follow-up of 92 months, overall survival of the allograft was an impressive 84.8%. A total of 15 patients (33%), however, had experienced at least one complication. Five allografts were revised for complications and one for local recurrence. The authors concluded that intercalary allografts augmented with intramedullary cement and compression plate fixation provide a reliable and durable method of reconstruction after the excision of a primary diaphyseal bone tumour. While it is unlikely that there will ever be a single benchmark in limb salvage and tumour reconstruction, given the variety of defects, primary diagnoses, and patient and surgeon expectations, this study does support the use of augmented intercalary allograft with cement and plate fixation. This technique is certainly one that has a place in modern orthopaedic oncology.
Non-vascularised fibular grafts for reconstruction of segmental and hemicortical bone defects following meta-/diaphyseal tumour resection of the limbs
One of the difficulties faced by tumour surgeons in limb reconstruction is that a relatively poor vascular supply causes difficulties with local flaps, and therefore causes restriction in the range of reconstructive options available. One option used is that of a fibular graft, either vascularised or not. It is certainly a matter of opinion whether or not vascular reconstruction is necessary in this setting, and if indeed this makes a difference in the long term. However, use of the vascularised option does, to a certain extent, dictate surgical availability, as the pedicle must be reconstructed with a suitable anastomosis. We were delighted to see this series of patients from Basel (Switzerland).2 The authors report 36 patients, all of whom were treated with non-vascularised fibula for segmental (n = 15) and hemicortical reconstructions (n = 21) after bone tumour resection (15 malignant, 21 benign) in the limbs. At a final mean follow-up of 8.3 years, union was achieved radiologically in 94% of patients, and 85% showed apparent hypertrophy at the graft-host junction. The overall complication rate was somewhat high at 36%, with four patients (11%) developing local recurrence. The authors report a relationship between the development of mechanical complications (fracture, delayed union/nonunion) and a defect size of ⩾ 12 cm. Encouragingly, the dual functional outcome was highly satisfactory (mean MSTS score 86%). The authors here concluded that non-vascularised fibular reconstructions should be considered a valuable alternative treatment option for patients with hemicortical defects or segmental reconstructions of less than 12 cm in which no additional neo-/adjuvant treatment is necessary. Reporting here a combination of segmental and hemicortical defects makes interpretation of these results somewhat more challenging than the average paper. Only six of the 36 cases received adjuvant therapy (which is on the low side for malignant tumours), hence their comment (based on their experience of six cases) that “this is a valuable addition ‘only’ in patients in which no additional neo-/adjuvant treatment is necessary”. This may be a bit overstated from the data. An important recommendation the authors do make, however, is that “Taking our own results into account, we therefore strongly recommend the use of vascularised fibula grafts for segmental bone defects of 12 cm or greater.” This can serve as a useful guideline in clinical practice.
Pasteurised autograft-prosthesis composite reconstruction may not be a viable primary procedure for large skeletal defects after resection of sarcoma
Among various types of composite biological reconstruction agents, pasteurised autograft-prosthesis composite (PPC) is popular when allograft is unavailable. The technique involves a combination of reconstruction using sterilised autograft and a megaprosthesis. The rationale is that, given time, the autograft will act as a framework and undergo creeping substitution, resulting in incorporation of the pasteurised autograft into the patient’s skeleton having eradicated the tumour. This review of 142 PPCs is a timely paper, casting light on the factors associated with the survival or failure of a PPC. Investigators in Seoul (South Korea) report the 20-year survival rate of 142 PPCs, which was a not terribly impressive 40%.3 Within the follow-up period of the series, 52 PPCs went on to fail. Patients in whom failure had occurred later underwent revision to a tumour prosthesis in about 40% and arthrodesis in 20%, and then 10% of each resulted in pseudarthrosis or amputation. The risks for failure in the series were larger tumours, longer lengths of pasteurised bone and, perhaps surprisingly, male gender. The results of this series are clearly well below expectations, both in terms of previous reports of similar techniques and compared with other limb salvage approaches. We wonder if surgeons would be better undertaking other types of limb salvage in patients with large defects, as it is difficult, based on these results, to recommend this as an acceptable approach.
Time to development of radiation-induced sarcomas: a multicentre study
Radiation-induced sarcomas (RIS) are a significant burden to patients and healthcare systems. However, very little is known about their development and its bearing on outcomes. Orthopaedic oncologists from Sydney (Australia) have presented their own large retrospective cohort study of radiation-induced sarcoma cases, which have been assembled from across five large international sarcoma centres.4 The paper focuses on the results of 419 patients, all presenting with a radiation-induced sarcoma. The study was designed to establish what the risk factors were for the development of RIS. The key findings were that that radiation in older age (hazard ratio (HR) 2.11) and chemotherapy for the first malignancy (HR 1.61) were independently associated with a shorter time to development of RIS. Subjects treated with chemotherapy had a median interval to RIS development of eight years, compared with 14 years in those who were chemotherapy-free, thus confirming an association between chemotherapy given for the first malignancy and a shorter time to development of RIS. The dose of radiotherapy was not associated with interval to RIS. One of the potentially significant confounding effects of this study is that patients may have been selected to receive combined modality treatment at diagnosis because they had a higher-grade, or more aggressive, primary malignancy in the first place, compared with those who did not have chemotherapy. These patients are more likely to have a mutation in tumour suppressor or DNA repair genes, which not only predisposes them to their aggressive primary cancer, but may also place patients at higher risk of, and with shorter timeframes to, development of a RIS.
Enchondromas and low-grade chondrosarcomas: perpetually confused?
One of the ongoing difficulties in orthopaedic oncology is in distinguishing between low-grade chondrosarcoma and enchondromas, with orthopaedic oncologists ever hopeful that novel MRI sequences will result in greater diagnostic accuracy. After all, an enchondroma is usually relatively innocent and a chondrosarcoma, low-grade or not, may not be. Colleagues in Birmingham (UK) have set out to identify the roles of clinical review, and conventional and dynamic contrast-enhanced MRI in making that key diagnostic distinction between enchondroma and chondrosarcomas of long bones.5 This paper focuses on the results of 60 patients, all with chondral tumours of various varieties. Based on final diagnosis, the cohort consisted of 27 enchondromas, ten cartilaginous lesions of unknown malignant potential, 15 grade 1 chondrosarcomas and eight high-grade chondrosarcomas. Clinical and imaging findings were compared with eventual histopathological grading. The distinguishing features between enchondromas and grade 1 chondrosarcomas were pain attributed to lesion, tumour length, endosteal scalloping, cortical destruction, bone expansion and soft-tissue mass. However, in this series, dynamic contrast-enhanced MRI could not make a distinction between enchondromas and grade 1 chondrosarcomas. This is essentially another paper showing how difficult it is to differentiate low-grade chondrosarcomas from enchondromas. We suspect this will be an ongoing and difficult problem, and it may be one that is never solved.
F-18 FDG PET perhaps the answer?
Staying with the theme of differentiating between benign and malignant cartilage tumours, this group from Miami, Florida (USA) undertook a comprehensive systematic review with the aim of quantifying the diagnostic accuracy of 18F-fluorodeoxyglucose Positron Emission Tomography / Computed Tomography (F-18 PET/CT) in discriminating between benign and malignant chondral lesions.6 The comprehensive review of literature identified 811 potential articles; however, just eight of these describing 166 lesions were included in the final review. The authors evaluated age, gender, tumour size, histologic grade, and maximum standardised uptake values (SUVmax) for each individual lesion and compared them with the outcomes of benign, low-grade intermediate and high-grade chondral neoplasms. Within this aggregate cohort, there were 101 patients with SUVmax values available, and 65 were therefore reported using aggregate data. The authors identified that benign tumours are more commonly found in females but that malignancy was not associated with patient age or size of lesion. With regard to the SUVmax results, PET/CT was able to distinguish between high-grade and low-grade tumours, however, it was much less useful in the division between benign and malignant lesions. In fact, with the mean SUVmax of 1.6 in benign lesions versus 2.0 in low-grade lesions, this really can be argued to be a non-discriminatory test. While we would not necessarily agree with the strongly positive conclusions reached by the authors of this paper regarding the use of PET/CT, this is not to say that PET/CT has no value, as clearly the data here would suggest that it can be used to distinguish between high-grade and other lesions. This paper supports the expected findings that SUVmax is higher with higher-grade lesions, but not helpful for differentiating between benign and low-grade cartilage lesions, but does it really matter?
Intralesional resection for central grade 1 chondrosarcoma
The confusion surrounding the diagnosis and management of chondrosarcoma is not restricted to the value of imaging modalities in reaching the diagnosis. There is again much debate on the best treatment methods - proponents of intralesional methods argue that this can be safely undertaken without the risk of morbidity associated with more extensive reconstructions and without exposing the patient to unnecessary risk of recurrence. These authors from Beijing (China) have published an updated review and meta-analysis with the aim of establishing whether there is an excess mortality associated with intralesional resection versus wide local margin resection in patients with central grade 1 chondrosarcoma.7 The authors were able to identify ten studies reporting the outcomes of 394 patients in the literature. This included 214 patients treated with intralesional resection and 180 patients treated with wide local excision. There were some surprisingly marked differences in the results. Patients treated with intralesional resection had a significantly lower complication rate and better functional outcomes. Reassuringly, there were no significant differences in terms of overall local recurrence. This paper essentially shows that, on the face of it, curetting out a grade 1 chondrosarcoma is safe. However, this does not take account of potential issues with patient selection, so patients with more ‘worrying’ features may well have undergone resection. The main concern is that if a low-grade chondrosarcoma recurs, it will do so at a higher grade and may then metastasise. This can take many years. A pinch of salt should therefore perhaps be taken when interpreting these results.
References
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