Validation of a Diagnostic Model to Differentiate Multiple Myeloma from Bone Metastasis.

Purpose: A diagnostic model to differentiate multiple myeloma (MM) from bone metastasis (BM) in patients with destructive bone lesions (MM-BM DDx) was developed to promote timely and appropriate referral of patients with MM to hematologists. External validation has never been conducted. This study aims to externally validate the performance of the MM-BM DDx model. Patients and Methods: This multi-center external validation study was conducted using retrospective data of patients over 45 years old diagnosed with MM or BM at six university-affiliated hospitals in Thailand from 2016 to 2022. The MM-BM DDx development dataset, including patients from 2012 to 2015, was utilized during external validation. Diagnostic indicators for MM included in the MM-BM DDx model are serum creatinine, serum globulin, and serum alkaline phosphatase (ALP). MM and BM diagnosis was based on the documented International Classification of Diseases 10th Revision codes. Model performance was evaluated in terms of discrimination, calibration, and accuracy. Results: A total of 3018 patients were included in the validation dataset (586 with MM and 2432 with BM). Clinical characteristics were similar between the validation and development datasets. The MM-BM DDx model's predictions showed an AUC of 0.89 (95% CI, 0.87, 0.90). The predicted probabilities of MM from the model increased concordantly with the observed proportion of MM within the validation dataset. The estimated sensitivity, specificity, and LR for each odds class in the validation dataset were similar to those of the development dataset. Conclusion: The discriminative ability and calibration of the MM-BM DDx model were found to be preserved during external validation. These findings provide support for the practical use of the MM-BM DDx model to assist clinicians in identifying patients with destructive bone lesions who are likely to have MM and enable them to arrange timely referrals for further evaluation by hematologists.

What Are the MSTS Scores and Complications Associated With the Use of Three-dimensional Printed, Custom-made Prostheses in Patients Who Had Resection of Tumors of the Hand and Foot?

BACKGROUND: There are a few good options for restoring bone defects in the hand and foot. 3D-printed implants have been used in the pelvis and elsewhere, but to our knowledge, they have not been evaluated in the hand and foot. The functional outcome, complications, and longevity of 3D-printed prostheses in small bones are not well known. QUESTIONS/PURPOSES: (1) What are the functional outcomes of patients with hand or foot tumors who were treated with tumor resection and reconstruction with a 3D-printed custom prosthesis? (2) What complications are associated with using these prostheses? (3) What is the 5-year Kaplan-Meier cumulative incidence of implant breakage and reoperation? METHODS: Between January 2017 and October 2020, we treated 276 patients who had tumors of the hands or feet. Of those, we considered as potentially eligible patients who might have extensive loss in their joint that could not be fixed with a bone graft, cement, or any prostheses available on the market. Based on this, 93 patients were eligible; a further 77 were excluded because they received nonoperative treatment such as chemoradiation, resection without reconstruction, reconstruction using other materials, or ray amputation; another three were lost before the minimum study follow-up of 2 years and two had incomplete datasets, leaving 11 for analysis in this retrospective study. There were seven women and four men. The median age was 29 years (range 11 to 71 years). There were five hand tumors and six tumors of the feet. Tumor types were giant cell tumor of bone (five), chondroblastoma (two), osteosarcoma (two), neuroendocrine tumor (one), and squamous cell carcinoma (one). Margin status after resection was ≥ 1 mm. All patients were followed for a minimum of 24 months. The median follow-up time was 47 months (range 25 to 67 months). Clinical data; function according to the Musculoskeletal Tumor Society, DASH, and American Orthopedic Foot and Ankle Society scores; complications; and survivorship of implants were recorded during follow-up in the clinic, or patients with complete charts and recorded data were interviewed on the telephone by our research associates, orthopaedic oncology fellows, or the surgeons who performed the surgery. The cumulative incidence of implant breakage and reoperation was assessed using a Kaplan-Meier analysis. RESULTS: The median Musculoskeletal Tumor Society score was 28 of 30 (range 21 to 30). Seven of 11 patients experienced postoperative complications, primarily including hyperextension deformity and joint stiffness (three patients), joint subluxation (two), aseptic loosening (one), broken stem (one), and broken plate (one), but no infection or local recurrence occurred. Subluxations of the metacarpophalangeal and proximal interphalangeal joints in two patients' hands were caused by the design of the prosthesis without a joint or stem. These prostheses were revised to a second-generation prosthesis with joint and stem, leading to improved dexterity. The cumulative incidence of implant breakage and reoperation in the Kaplan-Meier analysis was 35% (95% CI 6% to 69%) and 29% (95% CI 3% to 66%) at 5 years, respectively. CONCLUSION: These preliminary findings suggest that 3D implants may be an option for reconstruction after resections that leave large bone and joint defects in the hand and foot. Although the functional results generally appeared to be good to excellent, complications and reoperations were frequent; thus, we believe this approach could be considered when patients have few or no alternatives other than amputation. Future studies will need to compare this approach to bone grafting or bone cementation. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Tumor-to-bone distance and radiomic features on MRI distinguish intramuscular lipomas from well-differentiated liposarcomas.

BACKGROUND: To develop a machine learning model based on tumor-to-bone distance and radiomic features derived from preoperative MRI images to distinguish intramuscular (IM) lipomas and atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLSs) and compared with radiologists. METHODS: The study included patients with IM lipomas and ALTs/WDLSs diagnosed between 2010 and 2022, and with MRI scans (sequence/field strength: T1-weighted (T1W) imaging at 1.5 or 3.0 Tesla MRI). Manual segmentation of tumors based on the three-dimensional T1W images was performed by two observers to appraise the intra- and interobserver variability. After radiomic features and tumor-to-bone distance were extracted, it was used to train a machine learning model to distinguish IM lipomas and ALTs/WDLSs. Both feature selection and classification steps were performed using Least Absolute Shrinkage and Selection Operator logistic regression. The performance of the classification model was assessed using a tenfold cross-validation strategy and subsequently evaluated using the receiver operating characteristic curve (ROC) analysis. The classification agreement of two experienced musculoskeletal (MSK) radiologists was assessed using the kappa statistics. The diagnosis accuracy of each radiologist was evaluated using the final pathological results as the gold standard. Additionally, we compared the performance of the model and two radiologists in terms of the area under the receiver operator characteristic curves (AUCs) using the Delong's test. RESULTS: There were 68 tumors (38 IM lipomas and 30 ALTs/WDLSs). The AUC of the machine learning model was 0.88 [95% CI 0.72-1] (sensitivity, 91.6%; specificity, 85.7%; and accuracy, 89.0%). For Radiologist 1, the AUC was 0.94 [95% CI 0.87-1] (sensitivity, 97.4%; specificity, 90.9%; and accuracy, 95.0%), and as to Radiologist 2, the AUC was 0.91 [95% CI 0.83-0.99] (sensitivity, 100%; specificity, 81.8%; and accuracy, 93.3%). The classification agreement of the radiologists was 0.89 of kappa value (95% CI 0.76-1). Although the AUC of the model was lower than of two experienced MSK radiologists, there was no statistically significant difference between the model and two radiologists (all P > 0.05). CONCLUSIONS: The novel machine learning model based on tumor-to-bone distance and radiomic features is a noninvasive procedure that has the potential for distinguishing IM lipomas from ALTs/WDLSs. The predictive features that suggested malignancy were size, shape, depth, texture, histogram, and tumor-to-bone distance.

Robustness of Radiomic Features: Two-Dimensional versus Three-Dimensional MRI-Based Feature Reproducibility in Lipomatous Soft-Tissue Tumors.

This retrospective study aimed to compare the intra- and inter-observer manual-segmentation variability in the feature reproducibility between two-dimensional (2D) and three-dimensional (3D) magnetic-resonance imaging (MRI)-based radiomic features. The study included patients with lipomatous soft-tissue tumors that were diagnosed with histopathology and underwent MRI scans. Tumor segmentation based on the 2D and 3D MRI images was performed by two observers to assess the intra- and inter-observer variability. In both the 2D and the 3D segmentations, the radiomic features were extracted from the normalized images. Regarding the stability of the features, the intraclass correlation coefficient (ICC) was used to evaluate the intra- and inter-observer segmentation variability. Features with ICC > 0.75 were considered reproducible. The degree of feature robustness was classified as low, moderate, or high. Additionally, we compared the efficacy of 2D and 3D contour-focused segmentation in terms of the effects of the stable feature rate, sensitivity, specificity, and diagnostic accuracy of machine learning on the reproducible features. In total, 93 and 107 features were extracted from the 2D and 3D images, respectively. Only 35 features from the 2D images and 63 features from the 3D images were reproducible. The stable feature rate for the 3D segmentation was more significant than for the 2D segmentation (58.9% vs. 37.6%, p = 0.002). The majority of the features for the 3D segmentation had moderate-to-high robustness, while 40.9% of the features for the 2D segmentation had low robustness. The diagnostic accuracy of the machine-learning model for the 2D segmentation was close to that for the 3D segmentation (88% vs. 90%). In both the 2D and the 3D segmentation, the specificity values were equal to 100%. However, the sensitivity for the 2D segmentation was lower than for the 3D segmentation (75% vs. 83%). For the 2D + 3D radiomic features, the model achieved a diagnostic accuracy of 87% (sensitivity, 100%, and specificity, 80%). Both 2D and 3D MRI-based radiomic features of lipomatous soft-tissue tumors are reproducible. With a higher stable feature rate, 3D contour-focused segmentation should be selected for the feature-extraction process.

Novel CSF1R-positive tenosynovial giant cell tumor cell lines and their pexidartinib (PLX3397) and sotuletinib (BLZ945)-induced apoptosis.

Tenosynovial giant cell tumor (TGCT) is a mesenchymal tumor derived from the synovium of the tendon sheath and joints, most frequently in the large joints. The standard of care for TGCTs is surgical resection. A new targeting approach for treating TGCTs has emerged from studies on the role of the CSF1/CSF1 receptor (CSF1R) in controlling cell survival and proliferation during the pathogenesis of TGCTs. We established four novel cell lines isolated from the primary tumor tissues of patients with TGCTs. The cell lines were designated Si-TGCT-1, Si-TGCT-2, Si-TGCT-3, and Si-TGCT-4, and the TGCT cells were characterized by CSF1R and CD68. These TGCT cells were then checked for cell proliferation using an MTT assay and three-dimensional spheroid. The responses to pexidartinib (PLX3397) and sotuletinib (BLZ945) were evaluated by two-dimensional MTT assays. All cells were positive for α­smooth muscle actin (α­SMA), fibroblast activation protein (FAP), CSF1R, and CD68. Except for Si-TGCT-4, all TGCT cells had high CSF1R expressions. The cells exhibited continuous growth as three-dimensional spheroids formed. Treatment with pexidartinib and sotuletinib inhibited TGCT cell growth and induced cell apoptosis correlated with the CSF1R level. Only Si-TGCT-4 cells demonstrated resistance to the drugs. In addition, the BAX/BCL-2 ratio increased in cells treated with pexidartinib and sotuletinib. With the four novel TGCT cell lines, we have an excellent model for further in vitro and in vivo studies.

Three-dimensional printed, proximal phalangeal prosthesis with metatarsophalangeal joint arthroplasty for the treatment of a giant cell tumor of the fifth toe: The first case report.

INTRODUCTION: The majority of patients with bone sarcoma or an aggressive benign tumor of the toe can be successfully treated by amputation. However, limb-salvage surgery for toe tumors remains challenging. PRESENTATION OF CASE: A 26-year-old female presented with an enlarging mass on her right 5th toe. Imaging studies revealed an expansile osteolytic, destructive lesion of the proximal phalanx of the 5th toe with metatarsophalangeal (MTP) joint invasion. A biopsy specimen confirmed a grade 1, giant cell tumor of the bone. An en bloc resection of the proximal phalanx was performed, and the defect was reconstructed with a patient-matched, three-dimensional, printed titanium proximal phalanx endoprosthesis with an MTP joint extension. The postoperative course was uneventful. The patient has walked with full weight-bearing since early postoperatively. No local recurrence or metastases were evident. However, scar formation occurred after two years, causing an overriding toe deformity. DISCUSSION: This case represents the first use of a toe prosthesis with MTP joint reconstruction. The complex MTP structure with a preserved metatarsal head facilitates the effort to mimic normal weight-bearing. CONCLUSION: A three-dimensional printed prosthesis of the 5th toe is a viable alternative to a bone graft or amputation. However, to avoid stiffness and complications, further study is needed to improve the prosthesis design.

Use of warm Ringer's lactate solution in the management of locally advanced giant cell tumor of bone.

BACKGROUND: This study was conducted to discover the effectiveness and safety of using warm Ringer's lactate solution (RLS) as a local treatment in the management of locally advanced giant cell tumor of bone with marked soft tissue invasion, including nearby neurovascular bundles. PATIENTS AND METHODS: This was a longitudinal cohort study with an average follow-up period of 4.6 ± 0.3 years, ranging from 4.2 to 5.9 years. There were 21 patients (9 male and 12 female), with the ages of subjects ranging from 12 to 64 years. Eight patients (38 %) were tumor recurrence cases. Pathological fracture was found in 15 patients (71 %). After extended curettage, warm RLS (50 °C) was locally applied for 20 min. Bone stabilization and reconstruction were then performed. RESULTS: All patients survived the operation. No additional neurovascular injury resulting from the use of warm RLS was found. Patients who had neurological deficit before the operation experienced significant improvement in motor and sensory function during the follow-up period. Complication was found in one patient (5 %). Two patients (9.5 %), had tumor recurrence and 19 patients (90.5 %) were tumor-free with good to acceptable function. CONCLUSION: Use of warm Ringer's lactate solution as an adjunctive local treatment during intra-lesional curettage of giant cell tumor with locally soft tissue extension was found to be safe with relatively low recurrence rate. However, additional studies to identify the optimum thermoablation dose at each part of the body should be undertaken before this technique can be used as a standard treatment.

Prevalence of neuropathic pain after radical sacral chordoma resection: an observational cohort study with 10-year follow-up.

This study was carried out to discover the prevalence, characteristics and severity of neuropathic pain after wide resection of chordoma of the sacrum by the use of posterior approach. Patients who had chordoma of their sacrums and underwent wide resection via posterior approach, during 1990-2002, were followed up as a prospective cohort. Pain assessment was carried out in terms of onset, characteristics, intensity (numerical rating scale), response to pain medication and associated symptoms. The correlation between patients' biographic data, preoperative neuropathic pain, type and levels of surgery and pain were analyzed. There were 21 patients; 14 male and 7 female patients. Their ages ranged between 29 and 75 years. Subtotal sacrectomy was carried out in 9 patients and total sacrectomy was carried out in 12 patients. All patients survived the operation. Neuropathic pain was found in 11 patients (52.4%). Male patients and presentation of preoperative neuropathic pain were significantly related to postoperative neuropathic pain. The other factors were not related to the postoperative pain. Recurrent of severe pain with different characteristics after the operation might indicate tumor recurrent. Early detection of the pain and proper treatment could minimize pain intensity and improved pain management satisfaction.

Prevalence of primary spinal tumors: 15-year data from Siriraj Hospital.

OBJECTIVE: To determine prevalence, demographic data and clinical presentation of primary vertebral tumors. MATERIAL AND METHOD: A retrospective study of the primary spine tumor specimens from Siriraj bone tumor registry from 1996 to 2010. RESULTS: From the study, primary spinal tumors constituted 85 of 1,679 bone tumor cases (5.06%). The common benign spinal tumors were giant cell tumor and hemangioma. The common malignant spinal tumors were chordoma, chondrosarcoma, and osteosarcoma. The mean age ofpresentation was 44.68 years. Fifty-three percent of tumors occurred in females. Pain was the most common presenting symptom, occurring in 73.53% of malignant and 52.94% of benign tumors. Neurological involvement occurred in 25% of malignant tumor Malignant lesions predominated in the sacral region while the most common location ofbenign specimens was thoracic region. CONCLUSION: The present study was the first demographic study ofprimary spinal tumor in Thai showed variety of prevalence when compared with similar studies based on Western patients. Whether these results reflect differences in the population, race and data collection method.

The outcomes of treatment of giant cell tumor of bone around the knee.

BACKGROUND: Giant cell tumor of bone has been characterized as an aggressive benign bone tumor and commonly occurs at the distal femur and the proximal tibia. The recommended treatment has ranged from intralesional curettage to wide excision and the decision depends on severity of the tumor extent, rate of local recurrence,functional and morbidity outcomes. OBJECTIVE: To compare extended curettage and wide excision in Grade II-III giant cell tumor of bone around the knee with regard to their effectiveness in tumor control and complication. MATERIAL AND METHOD: There were 54 patients with a giant cell tumor which involved the distal femur or proximal tibia who had been managed consecutively at Siriraj Hospital between 1994-2009. The lesion of all patients were staged according to the system of Campanacci et al. There were 21 males and 33 females with mean age of 34 years. Thirty-five tumors located at distal femur and 19 located at proximal tibia. Fourteen patients had a Grade II lesion and 40 had a Grade III lesion. Thirty patients received extended curettage whereas other 24 patients had a wide excision. Fisher's exact analysis was used for statistical analysis for the outcome of tumor recurrence in each surgery. RESULTS: The mean follow-up time was 59 months. There were 7 (23.3 percent) local recurrences in the extended curettage group and 2 (8.3 percent) in the wide excision group. Most recurrences occurred within one year postoperatively. There was no statistical difference for the outcome of tumor recurrence in each group (p = 0.270). All patients with tumor recurrence were successfully treated with re-curettage, except for 3 patients who was treated by above-knee amputation. The functional analysis was excellence in the extended curettage group (94 percent) and good in the wide excision group (77.6 percent) according to the Musculoskeletal Tumor Society functional classification. CONCLUSION: The authors believe that using extended curettage was not significantly different in percentage of local recurrence when compared with wide excision for Campanacci's Grade II-III of giant cell tumor of bone. Even better function was found in extended curettage group, the choice of surgical treatment should be considered in individual patient which depends on the extent of bone destruction and risk of tumor recurrence.

In vitro effects of thermoablation on apoptosis of giant cell tumor of bone: a preliminary report.

BACKGROUND: Giant cell tumor of bone is a common benign aggressive bone tumor. Recurrent rate in the patients who have the tumor with soft tissue invasion is rather high. Use of strong chemicals such as phenol and liquid nitrogen to lessen the recurrent rate might not be used in this lesion. OBJECTIVE: The experiment was carried out to discover apoptotic effects of thermoablation on giant cell tumor of bone to find out a possibility to use thermoablation in the clinic in the patients with extensive lesion. MATERIAL AND METHOD: Tumor cell suspension was prepared from 4 patients who had definite diagnosis of giant cell tumor of bone. The tumor cells were subjected to thermoablation at 45, 47 and 50 degrees C for 10 to 30 minutes before were cultured at 37 degrees C for another 3 days. Osteoblasts and chondrocytes from the last 3 patients were collected,prepared and underwent thermoablation in the same fashion. Apoptosis of tumor cells, chondrocytes and osteoblasts were carried out by the use of flow cytometry. RESULTS: Thermoablation at 47 degrees C for 30 minutes resulted in < 50% chondrocyte and osteoblast apoptosis and 70-90% tumor cells apoptosis of 3/4 patients. Thermoablation at 47 and 50 degrees C for 20 to 30 minutes has more negative effect on giant cell tumor of bone than chondrocytes and osteoblasts. CONCLUSION: Thermoablation might be a useful tool for local tumor control in the clinic.

Factors of local recurrence of giant cell tumor of long bone after treatment: plain radiographs, pathology and surgical procedures.

BACKGROUND: To evaluate the relationship between local recurrence of giant cell tumor (GCT) after surgical treatments and plain radiography, pathology grade and surgical procedures. MATERIAL AND METHOD: Patients with pathologically proven primary giant cell tumor of long bones, who underwent surgical treatment in Siriraj Hospital between 1995 and 2007, were retrospectively reviewed. Plain radiographic findings were reviewed by an experienced musculoskeletal radiologist without knowledge of the clinical history or pathologic results. Specific attention on plain radiographic evaluations included site of tumor in long bone, total tumor volume, expansion of cortex, breaking of cortex, and presence of pathological fracture. Patients with grade III tumor were excluded due to malignant histology. Patients received treatments with amputation were also excluded due to no possibility of tumor recurrence. Only patients who received surgical treatments with wide excision or curettage with cement were included in the present study. Univariate analysis and Cox proportional hazard ratio was used to evaluate the influence of plain radiographic findings and histology grade on risk of tumor recurrence. RESULTS: Seventy-four patients participated in this study and included 32 males (43%) and 42 (57%) females with a mean age of 35 years (range 17 to 84). The median follow-up time was 3.2 years. Forty-eight patients (65%) underwent curettage with cement or bone graft and 26 patients (35%) underwent wide excision. Sixty-three patients (85%) did not develop tumor recurrence while 11 patients (15%) developed local recurrent tumor. Those occurred only in patients who underwent curettage with cement or bone graft. None of the patients who underwent wide excision developed local recurrence. Median of time after operation to recurrence was 3.5 years (range, 0.5 to 10.3 years). Local recurrence occurred in the distal femur in five patients (45%), in the proximal tibia in five patients (45%), and in distal radius in one patient (9%). Risk of local recurrence of GCT was not statistically different in patients with any abnormal features of plain radiography as well as histology grade. CONCLUSION: No radiographic findings and histological grade of GCT can predict tumor recurrence after curettage procedure. Compared with wide excision, risk of local recurrence in patients that received treatment with curettage was significantly higher. However the choice of treatment should be balanced between preserving maximal joint function and risks of tumor recurrence.

Functional outcome following excision of a tumour and reconstruction of the distal radius.

We retrospectively studied the functional and oncological results of 15 patients after reconstruction of the distal radius with osteoarticular allograft or non-vascularised fibular graft following wide excision of an aggressive benign or malignant tumour. Eight patients underwent osteoarticular allograft and seven patients had a non-vascularised autogenous fibular graft reconstruction. The average time for incorporation of the graft was 6 and 5 months in each reconstruction respectively. There was no tumour recurrence after follow up over 41.5-95.5 (average 60.5) months. All patients had good and excellent functional results. Three patients in the group reconstructed with osteoarticular allograft had plate loosening and graft fractures which were successfully treated subsequently.

The results of surgical management of bone metastasis involving the periacetabular area: Siriraj experience.

BACKGROUND: Periacetabular metastasis is a common site of bone metastasis and can cause major disability to the patients. Non-operative treatment including medication or radiation therapy is the first treatment modality. The operative treatment is indicated in patients with failed non-operative treatment or pathologic fracture. OBJECTIVE: To assess the functional results, quality of life, and complications after reconstruction of the periacetabular metastasis. MATERIAL AND METHOD: Fourteen patients underwent 16 intralesional excisions of tumor and cemented total hip arthroplasty reconstruction from 2002 to 2006. The primary tumors were breast carcinoma in five patients, thyroid carcinoma in three, kidney carcinoma in two, and one each of cervix carcinoma, urinary bladder carcinoma, lung carcinoma, and multiple myeloma. Type of periacetabular metastases by Harrington 's classification, age of patients, blood loss, unit of blood transfusion, and postoperative complication were reviewed. Pre- and Postoperative pain by the visual analogue scale was evaluated. RESULTS: The mean age of patients was 56years with a mean follow up time of 389 days (range 30-1,275 days). The mean time from diagnosis of primary tumor to periacetabular metastatic surgery was 32.5 months (range 0-84 months). By Harrington 's classification, seven patients were classified in class I, four patients were class II, and three patients were class III. The visual analogue scale was improved from more than 8/10 preoperatively to 2/10 postoperatively. All patients could ambulate and walk independently and two patients could walk without gait support. Four patients died of disease progression and 10 patients are still alive. Two patients had complications from postoperative hip dislocation and acetabular loosening which successfully treated by closed reduction and revision of the prosthesis respectively. CONCLUSION: With promising results, low rate of complication and improvement of quality of life could be achieved after total hip arthroplasty reconstruction in the appropriately selected patient with a periacetabular metastasis. Additional surgery may be required in the patient with longer survival or progression of the disease.

Endoprosthetic reconstruction for malignant bone and soft-tissue tumors.

BACKGROUND: Nowadays, the results of the management of malignant bone and soft-tissue tumors have been dramatically improved because of the advance in imaging, chemotherapy, radiation therapy, and surgical techniques. Patients can have longer survival times with limb-salvage surgery. Several techniques of reconstruction have been advocated and gained more popularity following malignant tumor resection by using allograft, tumor prostheses, composite allograft prosthesis, or arthrodesis. OBJECTIVE: To report the preliminary results of 32 endoprosthetic reconstructions following malignant bone and soft-tissue tumor resection. The oncologic results, functional outcomes, and complications from the surgery were assessed in the present study. MATERIAL AND METHOD: Since September 1988, the authors have performed 188 limb-salvage surgical operations for the treatment of musculoskeletal tumors at Siriraj Hospital. From March 1994 to July 2006, 32 endoprosthetic reconstructions were performed on 30 patients following malignant bone or soft-tissue tumor removal. There were 16 males and 14 females with a mean age of 28 years (range 10-73). The diagnosis was conventional osteosarcoma in 16 patients, parosteal osteosarcoma in two patients, chondrosarcoma in two patients, leiomyosarcoma in two patients, failed allograft in two patients and one patient each of periosteal osteosarcoma, Ewing's sarcoma, Gorham's disease, synovial sarcoma, malignant fibrous histiocytoma, metastatic renal cell carcinoma, and prosthetic loosening. Wide excision was performed with a mean length of 18.5 cm (range 10-41). Five proximal femurs, 17 distal femurs, 1 total femur 3 proximal tibias, 1 intercalary tibia, 4 proximal humerus and 1 distal humerus were used for reconstruction. Modular replacement systems (MRS, Stryker/Howmedica/Osteonics) were the most common prostheses used in the present series. RESULTS: The mean follow-up time was 26 months (range 6-128.7). Sixteen patients are continuously free of the disease, two are alive with the disease, two had no evidence of the disease, nine died of the disease, and one patient died from complication of hypertension. The mean Musculoskeletal Tumor Society functional analysis for upper extremity reconstruction was 93% (range 86.7-100) and for lower extremity was 89% (range 63.3-100). Two patients (6.7%) were determined to be a failure. Revision due to aseptic loosening was performed in one patient (3.3%) and one hip disarticulation was done related to local recurrence (3.3%). One patient with sciatic nerve palsy and two seromas was found and successfully treated in the present study. CONCLUSION: Endoprosthetic reconstruction could yield satisfactory results as a wide excision and limb-salvage for patients with malignant bone and soft-tissue tumors. Most patients in the present report had good to excellent functions following surgery and few complications occurred in the present report.

Effects of screw eccentricity on the initial stability of the acetabular cup.

One of the major failure modes of cementless acetabular components is the loosening of the acetabular cup, which is mostly attributable to insufficient initial stability. A hemispherical cup with a porous coating which is inserted with press-fit fixation and secured with several screws is one of the most widely used approaches. Many studies have found that bone screws are very helpful aids for cup fixation, but the optimal surgical technique for inserting screws has not been clearly reported. In this study, hemispherical cups were fixed into blocks of foam bone with zero to three screws. The effects of three types of screw eccentricity (a 1-mm offset and angular eccentricities of 15 degrees and 25 degrees ) on the initial stability of the acetabular cup were evaluated. The experimental results indicate that increasing the number of screws enhances the cup stability in the case of ideal screwing (i.e., with no eccentricity). An angular eccentricity of 15 degrees did not affect the cup stability for fixation with one or two screws. However, the presence of 25 degrees of angular eccentricity significantly reduced the stability of the cup, while 1 mm of offset eccentricity produced an even greater impact.

Mechanical effects of partial sacrectomy: when is reconstruction necessary?

We examined the mechanical consequences of high partial transverse sacrectomy. Ten human cadaveric pelves were randomly assigned to three groups. In the Control Group, the sacrum was left entirely intact. In Group I, transverse partial sacrectomy was performed just caudal to the S1 neural foramina. In Group II, transverse partial sacrectomy was performed just cephalad to the S1 neural foramina. Each pelvis was mounted on a testing apparatus and loaded vertically at the L4/L5 disk space until failure occurred. The average resection of the sacroiliac joints was 16% in Group I, and 25% in Group II. The average load to failure was 3014 N in the Control Group, 2166 N in Group I, and 1045 N in Group II. The average stiffness was 353 N/mm in the Control Group, 222 N/mm in Group I, and 100 N/mm in Group II. All specimens failed because of fractures through the sacrum (mostly Denis Zone II) in the sagittal plane. Using the literature to predict normal forces at the lumbosacral junction, we suggest Group I pelves could withstand postoperative mobilization without fracture, whereas Group II would probably not. Reconstruction should therefore be considered when performing transverse partial sacrectomy above the S1 nerve root.