Subchondral cysts of the tibia secondary to osteoarthritis of the knee are not usually seen on radiographs. When present, they are typically small and present no diagnostic difficulty. Two cases of unusually large subchondral lesions of the medial tibial plateau are presented. The lesions were well defined and lay adjacent to the medial tibial cortex with their long axes in the sagittal plane. Both were associated with moderate medial compartment osteoarthritis. Additional information obtained from computed tomography indicated that these lesions were subchondral cysts secondary to osteoarthritis rather than tumors or other tumor-like conditions.

Objective

Fibrous dysplasia is a benign disorder of bone that can cause cortical thinning as well as bony expansion. Full-thickness cortical bony destruction, however, typically characterizes more aggressive or malignant lesions of bone. We present three cases of fibrous dysplasia that illustrate this more aggressive and potentially confusing feature.

Materials and methods

The findings on radiography and cross-sectional imaging studies are reviewed in three surgically proven cases of fibrous dysplasia that exhibited full-thickness cortical bony destruction.

Results

Well-defined cortical perforations without associated periosteal reaction were clearly seen on CT. This finding was suspected on plain radiography in only one of the three cases. A small associated soft tissue mass was detected by MR imaging in this case. Many cortical perforations were seen in the one case of polyostotic fibrous dysplasia.

Conclusion

Full-thickness cortical bony destruction can be seen in fibrous dysplasia. This finding, which may only be evident on cross-sectional imaging studies, should not by itself alter a diagnostic impression of fibrous dysplasia supported by other radiographic and clinical features.

Background

The majority of published functional outcome data for tumor megaprostheses comes in the form of subjective functional outcome scores. Sparse objective data exist demonstrating functional results, activity levels, and efficiency of gait after endoprosthetic reconstruction in patients treated for orthopaedic tumors. Patients embarking on massive surgical operations, often in the setting of debilitating medical therapies, face mortality and a myriad of unknowns. Objective functional outcomes provide patients with reasonable expectations and a means to envision life after treatment. Objective outcomes also provide a means for surgeons to compare techniques, rehabilitation protocols, and implants.

Questions/purposes

We asked the following questions: (1) What is the efficiency of gait (ie, oxygen consumption) at final recovery from endoprosthetic reconstruction for oncologic resections? (2) What is the knee strength after lower extremity endoprosthetic reconstruction as compared with the contralateral limb? (3) How active are patients with tumor megaprostheses at home and in the community?

Methods

Sixty-nine patients with endoprosthetic reconstructions for primary lower extremity bone sarcoma met inclusion criteria and were invited by mailing to undergo oxygen cost study and strength testing. Twenty-four patients (seven proximal femoral replacements, nine distal femoral replacements, and eight proximal tibia replacements) underwent evaluation in the gait laboratory at a mean of 13.2 years after their reconstruction. All patients were then asked to wear step activity monitors at home and in the community for 7 consecutive days.

Results

Median O2 consumption (in mL/kg/m) among the endoprothesis groups was not different from the control patients with the numbers available (proximal femoral replacement 0.17, distal femoral replacement 0.16, proximal tibia replacement 0.18, control 0.15, p = 0.21). With the numbers available, there was no difference in walking speed as compared with the control group (proximal femoral replacement 1.20 m/s, distal femoral replacement 1.27 m/s, proximal tibia replacement 1.12 m/s, control 1.27 m/s, p = 0.08). Patients with proximal tibia replacements had reduced knee extension and flexion strength compared with patients in other reconstruction groups (84% reduction in extension versus those with proximal femoral replacements, 35%, and distal femoral replacement, 53%, p = 0.001, and 43% reduction in flexion versus proximal femoral replacement, 11%, distal femoral replacement, 2%, p = 0.006). With the numbers available, mean strides per day were not different among the reconstruction groups (proximal femoral replacement = 4709 strides/day [3094-6696], distal femoral replacement = 2854 [2461-6015], and proximal tibia replacement = 4411 [3093-6215], p = 0.53).

Conclusions

Although knee strength was reduced in patients with proximal tibia replacements compared with femoral reconstructions, all groups had an efficient gait and were active at home and in the community at a mean of 13.2 years after surgery. Despite the magnitude of these surgeries, these patients are similarly active as patients after standard total hip arthroplasty. These findings provide objective data from which patients undergoing tumor megaprosthesis reconstructions of the lower extremity can reasonably base expectations of efficient gait and active lifestyles outside of the hospital setting. These data may provide hope and long-term goals for patients facing the uncertainty of chemotherapy and surgical treatment.

Level of evidence

Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

As the life expectancy of patients with musculoskeletal tumors improves, long-term studies of endoprosthetic reconstructions are necessary to establish realistic expectations for the implants and compare them to other reconstruction approaches. (1) What is the long-term survival of cemented bipolar proximal femoral replacements? (2) How does prosthesis survival compare to patient survival among patients with Stage I, II, and III disease? (3) Do modular implants outperform custom-built prostheses? (4) Do some proximal femoral replacements require conversion to THA? We retrospectively reviewed all 86 proximal femoral replacements used for tumor reconstruction from 1982 to 2008. Primary diagnoses were 43 high-grade tumors (IIA/IIB), 20 low-grade tumors (IA/IB or benign), and 23 with metastatic disease. We reviewed prosthesis survival, patient survival, complication rates, functional outcomes, and rates of conversion to THA. Five of 86 patients (5.8%) required revision of the femoral component. Five-, 10-and 20-year implant survivorships were 93%, 84%, and 56%, respectively. All patients with low-grade disease survived; the 5-year survival rate for patients with metastatic disease was 16%; the 5-, 10-, and 20-year survival for IIA/IIB patients was 54%, 50%, and 44%, respectively. Five of 86 patients (5.8%) underwent conversion to THA for groin pain. Cemented bipolar proximal femoral replacements after tumor resection proved a durable reconstruction technique. The implants outlived patients with metastatic disease and high-grade localized disease while patients with low-grade disease outlived their implants. The survival of modular prostheses was comparable to that of older, one-piece custom designs. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

A case has been presented of a 14-year-old male patient who developed a fusiform mass on the volar aspect of his left forearm following two fractures. Microscopic features and plain radiography, CT, and MRI appearance of juxtacortical aggressive fibromatosis are discussed.

Although magnetic resonance (MR) imaging is highly sensitive for the detection of abnormalities of the musculoskeletal system, changes in marrow and soft-tissue signal intensity are often nonspecific, and benign conditions may be mistaken for malignancy. In an effort to identify the cause of this type of misdiagnosis in MR examinations, the MR scans were reviewed of 30 patients whose images manifested bone and/or soft-tissue changes that were initially believed to be consistent with malignancy but were later found to represent benign conditions. Of the 30 patients, MR abnormalities were attributable to trauma in 11, benign tumors and tumorlike conditions in ten, infection in seven, and prior radiotherapy in two. In 24 cases, correlative imaging studies (14 patients), appropriate clinical history (six patients), and/or physical and laboratory examinations (four patients) would have avoided these misdiagnoses.

This 9-year-old girl presented with a painful mass in the posterolateral aspect of her right knee. Excisional biopsy of the mass revealed a juxta-articular myxoma. The differential diagnosis for such an intra- or periarticular mass should include meniscal cyst, parameniscal cyst, ganglion cyst, juxta-articular myxoma, focal nodular PVNS, and desmoid tumor. Current imaging techniques do not allow differentiation between these benign lesions and low grade myxoid-containing sarcoma.

Advocates of newer implant designs cite high rates of aseptic loosening and failure as reasons to abandon traditional cemented endoprosthetic reconstruction of the distal femur. We asked whether newer, modular distal femoral components had improved survivorship compared with older, custom-casted designs. We retrospectively reviewed 254 patients who underwent distal femoral endoprosthetic reconstruction. We excluded two patients with cementless implants, 27 with expandable prostheses, and 39 who had a nontumor diagnosis. This left 186 patients: 101 with older custom implants and 85 with contemporary modular implants. The minimum followup was 1 month (mean, 96.0 months; range, 1–336 months). The tumor was classified as Stage IIA/IIB in 122 patients, Stage IA/IB or benign in 43, and Stage III or metastatic in 21. Kaplan-Meier analysis revealed overall 10-, 20-, and 25-year implant survival rates of 77%, 58%, and 50%, respectively, using revision of the stemmed components as an end point. The 85 modular components had a greater 15-year survivorship than the 101 custom-designed implants: 93.7% versus 51.7%, respectively. Thirty-five stemmed components (18.8%) were revised for aseptic loosening in 22 patients, implant fatigue fracture in 10, infection in two, and local recurrence in one. Cemented modular rotating-hinge distal femoral endoprostheses demonstrated improved survivorship compared with custom-casted implants during this three-decade experience. Patients with low-grade disease and long-term survivors of high-grade localized disease should expect at least one or more revision procedures in their lifetime. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.