Objective To evaluate the effects of sacrectomy extent on the stabil ity of lumbo-il iac fixation using single or dual il iac screw technique, and to determine which conditions require the dual il iac screw technique. Methods Nine fresh L2 to pelvic specimens were harvested from donated adult cadavers. After testing the intact state simulated by L3-5 pedicle screw fixation, sequential partial sacrectomies and L3 to il iac fixation using bilateral single il iac screw (Single) wereconducted on the same specimen as follows: in group A, under S1 partial sacrectomy and Single; in group B, under 1/2 S1 partial sacrectomy and Single; in group C, one-side (left) sacroil iac joint resection and Single; in group D, total sacrectomy and Single; and in group E, the single il iac screw was replaced by dual il iac screws based on group D. Biomechanical testing was performed on a material testing machine under 0-800 N compression and —7-7 N•m torsion loading modes for construct stiffness evaluation. Results The compressive stiffness of intact condition was (392 ± 119) N/mm, groups A, B, C, D, and E obtained 106.4% ± 9.5%, 102.7% ± 8.0%, 92.2% ± 10.1%, 72.7% ± 8.0%, and 107.7% ± 10.7% of intact condition, respectively. No significant differences were found among groups A, B, C, and the intact state (P gt; 0.05), however, the four groups showed significantly higher compressive stiffness than group D (P lt; 0.05). Although group E exhibited a comparable compressive stiffness with groups A, B, and intact state (P gt; 0.05), it displayed markedly higher compressive stiffness than groups C and D (P lt; 0.05). The torsional stiffness of intact state was (3.22 ± 1.23) N•m/deg. Groups A, B, C, D, and E acquired 105.4% ± 10.1%, 89.8% ± 12.3%, 75.9% ± 10.6%, 71.2% ± 10.2%, and 109.1% ± 16.9% of intact state, respectively. No significant differences were detected among groups A, B, E, and the intact state (P gt; 0.05). However, groups C and D showed remarkably lower torsional stiffness than groups A, E, and the intact state (P lt; 0.05). Importantly, group E offered remarkably higher torsional stiffness than group B (P lt; 0.05). Conclusion After under 1/2 S1 partial sacrectomy, single il iac screw technique could effectively restore local stabil ity; whereas it could hardly provide adequate stabil ity for further resection of one-side sacroil iac joint or total sacrectomy; in such situation, the use of dual il iac screw technique could obtain sufficient construct stabil ity. Therefore, in the surgical treatment of sacral tumor, the dual il iac screw technique should be considered for the unstable conditions of totalsacrectomy or under 1/2 S1 sacrectomy with one-side sacroil iac joint resection.
Objective To compare the maximum pull-out strength of the upper il iac screw and lower il iac screw with and without polymethylmethacrylate (PMMA) augmentation, and to provide the experimental evidences for the rational use of il iacscrews. Methods Ten intact human il ium from 5 donated cadavers with formal in embalmed were selected. The bone mineral density (BMD) of L1-4 of each cadaver was measured with a dual energy X-ray absorptiometry. The screws placed in the upper and lower il iac column were named as the upper and lower il iac screw, respectively. Using 70 mm length and 7.5 mm diameter screws with and without PMMA augmentation, 4 il iac screw technique models were sequentially establ ished and tested as follows: upper il iac screw (group A), upper il iac screw with PMMA augmentation (group B), lower il iac screw (group C), and lower il iac screw with PMMA augmentation (group D). Each il ium was mounted on a material testing machine with its position similar to standing. Under 2 000 cycl ic compressive loadings of 100-300 N to the screw, the maximum pull-out strength of il iac screw was measured. Results The BMD value of the 5 human cadavers was (0.88 ± 0.06) g/cm2. All the il iac screws were inserted into the screw tracts accurately as expected. No screw penetrations of acetabulum or cortex was not observed through visual inspection. There was no “halo” ring sign surrounding any screw after the 2 000 cycle loading. The maximum pull-out strengths of groupsA, B, C, and D were (964 ± 250), (1 462 ± 266), (1 537 ± 279), and (1 964 ± 422) N, respectively. Group D exhibited the highest maximum pull-out strength among the 4 groups (P lt; 0.05). No significant difference was detected between groups B and C (P gt; 0.05); however, groups B, C showed higher maximum pull-out strength than group A (P lt; 0.05). Conclusion The lower il iac screw offers significantly higher fixation strength than the upper il iac screw; PMMA augmentation could effectively increase the fixation strength of il iac screws and therefore could be appl ied in the salvage of il iac screw loosening.
Objective To evaluate the effectiveness of prosthetic revision using custom-made long stem prosthesis and allograft-prosthesis composite (APC) for aseptic loosening after bone tumor resection. Methods Between January 2002 and June 2008, 14 patients with aseptic loosening after bone tumor resection were treated. There were 8 males and 6 females,aged 21-70 years (mean, 43.9 years). The locations were distal femur (8 cases), proximal femur (2 cases), and proximal tibia (4 cases). Pain of the affected l imb occurred after 6-31 years of prosthesis replacement and worsened when bearing and walking; 6 patients had shortened l imb. The functional results were assessed quantitatively according to the functional rating system of the Musculoskeletal Tumor Society (MSTS). The MSTS score was 16.36 ± 1.50 before revision. The X-ray films showed obvious prosthetic loosening and subsidence. The average time of symptom was 4.5 years (range, 3-9 years). In 7 patients having severe bone loss (the decrease of the thickness of cortical bone was more than 50%) and the prosthetic subsidence was more than 2 cm, the revision operation with the APC was performed; in 7 patients having less bone loss (the decrease of the thickness of cortical bone was less than 50%), the custom-made long stem prosthesis was performed. Results All wound healed by first intention. Two patients had temporary peroneal nerve paralysis and recovered after 3 months. All the patients were followed up 3.6 years on average (range, 2 years and 2 months-7 years) after revision. After revision, pain was rel ieved and the range of joint was improved. The MSTS score was 23.43 ± 2.56 at 12 months after revision showing significant difference when compared with the preoperative score (t=8.910, P=0.024). The X-ray films showed that lucency space l ine around stem cement in 2 patients at 12 months, and no prosthesis loosening and infection occurred. Conclusion The prosthetic revision after l imb salvage surgery with prosthesis for bone tumors was acceptable. The good functional results can be achieved by the revision with the APC or the custom-made long stem prosthesis according to the bone loss.
Objective To evaluate the cl inical outcomes of the wide resection and the functional reconstruction for treating mal ignant tumors of the proximal femur. Methods The cl inical data were analysed from 62 patients with mal ignant tumors of the proximal femur treated between January 1987 and December 2007. There were 29 males and 33 females with a median age of 35 years (range, 14-73 years). In 41 patients with primary mal ignant tumors having a disease course of 0.5-14.0 months, there were 16 cases of osteosarcoma, 7 cases of fibrosaroma, 6 cases of chondrosarcoma, 6 cases of mal ignant fibrous histiocytoma, 4 cases of mesenchymal sarcoma,1 case of Ewing sarcoma, and 1 case of angiosarcoma, including 3 cases of type IB, 2 cases of type IIA, 35 cases of type IIB, and 1 case of type III according to Enneking stage. In 21 patients with metastatic tumors, 16 had a mal ignant tumor history; the disease course was 0.1-28.0 months (3.4 months on average). Radical resection was performed in 9 cases, extensive resection in 39 cases, and marginal resection in 14 cases. After resection, 39 cases underwent reconstruction with prostheses (prostheses group) and 14 cases underwent reconstruction with allograft-prosthetic composites (APC, APC group). Results All incision healed by first intention. Twenty-six cases died of tumor metastasis,their postoperative survive time was 16-56 months (28 months on average). The average follow-up time was 64 months (range, 28-221 months) in 36 survival patients. The local recurrence rate of primary mal ignant tumors was 4.88% (2/41). In prostheses group, dislocation of femoral head occurred in 2 cases, fracture of prosthetic stem in 1 case, hip pain in 3 cases, acetabular wear in 3 cases, and stem loosening in 5 cases. In APC group, nonunion of APC occurred in 3 cases and acetabular wear in 1 case. At last follow-up, the average Musculoskeletal Tumor Society (MSTS) functional scores were 77.69% ± 6.50% in prostheses groupand 85.71% ± 7.45% in APC group, showing significant difference (P lt; 0.001). Conclusion When the wide resection isperformed for mal ignant tumors of the proximal femur, better local control could be achieved. Compared with econstruction of the prosthesis, the APC reconstruction can provide better function.