The functional evaluation of patients with primary malignant tumours about the knee treated by modular endoprosthetic replacement

Tibial Growth Disturbance Following Distal Femoral Resection and Expandable Endoprosthetic Reconstruction

BACKGROUND

In growing children, an expandable endoprosthesis is commonly used after distal femoral resection to compensate for loss of the distal femoral physis. Our hypothesis was that such prostheses can affect proximal tibial growth, which would contribute to an overall leg-length discrepancy and cause angular deformity.

METHODS

Twenty-three skeletally immature patients underwent the placement of a distal femoral expandable endoprosthesis between 1994 and 2012. Tibial length, femoral length, and mechanical axis were measured radiographically to determine the growth rate.

RESULTS

No patient had radiographic evidence of injury to the proximal tibial physis at the time of surgery other than insertion of the tibial stem. Fifteen (65%) of the patients experienced less proximal tibial growth in the operative compared with the contralateral limb. In ten (43%) of the patients, the discrepancy progressively worsened, whereas in five (22%) of the patients, the discrepancy stabilized. Seven patients did not develop tibial length discrepancy, and one patient had overgrowth of the tibia. For the ten patients with progressive shortening, the proximal tibial physis grew an average of 4.0 mm less per year in the operative limb. Five (22%) of the patients had ≥ 20 mm of tibial length discrepancy at last follow-up. Three of these patients underwent contralateral tibial epiphysiodesis. Three patients required corrective surgery for angular deformity.

CONCLUSIONS

The tibial growth plate may not resume normal growth after implantation of a distal femoral prosthesis. Physeal bar resection, prosthesis revision, and contralateral tibial epiphysiodesis may be needed to address tibial growth abnormalities.

A biomechanical evaluation of press-fit stem constructs for tumor endoprosthetic reconstruction of the distal femur

This study was designed to assess the biomechanical parameters of the older Kotz Modular Femur Tibia Reconstruction (Stryker Inc, Mahwah, NJ) stem and the newer Restoration and the unfluted Global Modular Replacement System (Stryker Inc, Mahwah, NJ) uncemented stems for use with tumor endoprostheses as well as to assess the optimal reaming technique for insertion of these stems. Fresh-frozen adult femora or composite distal femora were implanted with the uncemented stems. Separate experiments were performed to compare reaming technique and bone resection level. All constructs were mechanically tested for axial compression, lateral bending, and torsional stiffness and torque to failure. Results showed that the biomechanical performance of all the stems were similar with respect to each parameter. Cylindrical reaming was associated with a significantly higher torque to failure than flexible reaming in the diaphysis (P = .006). Newer uncemented stems provide adequate initial biomechanical stability for implantation in the distal femur.

Revision of tumor prosthesis of the knee joint

Background

Among 40 patients with primary malignant tumors of the knee joint who underwent reconstruction of the affected limb with tumor prosthesis, revision was required in 7 due to stem breakage or loosening.

Subjects and methods

In the 7 cases undergoing revision, conditions and background factors at the time of breakage, the breakage site, time of revision, models of previous and new prostheses, stem diameters before and after revision, details of the revision (blood loss, operative time), and the presence or absence of adjuvant therapy were determined.

Results

The replacement site was the distal femur in 5 and proximal tibia in 2. Revision was performed 6 years and 2 months after the previous prosthesis placement on average. The broken prosthesis model was KMFTR in 4 and HMRS and the physio-hinge type in one each. Revision due to loosening was performed in a case requiring replacement with Growing Kotz prosthesis. The model was switched to HMRS in 3, and the stem diameter was changed to 12 mm in 3 KMFTR breakage cases. The mean stem diameters were 11.2 and 10.2 mm in the non-revision and revision groups. The respective resection rates were 36 and 45%. The mean functional evaluation was 70.1% before and 76.2% after revision.

Conclusion

To reduce the risk of tumor prosthesis breakage, the amount of bone resection should be limited to 30% or less in the affected bone, the stem diameter should be at least 12 mm, and the stem shape should be fitted to the anatomical shape of the femur.

Short and long term failure of the modular oncology knee prosthesis

This retrospective study investigated the modes of implant failure in 80 patients with modular oncology knee prostheses. Twenty patients (25%) required revision: 12 (60%) for stem loosening, 6 (30%) for bearing failure, and 2 (10%) for infection. Patients with bone sarcomas survived longer; however, long-term prosthetic survivorship was a problem. A higher failure rate was found in patients with tibial tumors and with adjuvant treatment of chemotherapy. This study demonstrates for improved long-term survivorship of modular oncology knee prostheses, there must be improvement in the methods of stem fixation, prosthetic materials, and bearing mechanics.

Aseptic loosening is uncommon with uncemented proximal tibia tumor prostheses

Aseptic loosening is a frequent cause of failure of cemented proximal tibia tumor endoprostheses. Uncemented prostheses may lessen this risk. We identified complications including aseptic loosening that affected prosthetic survival, limb survival and functional outcome for 44 consecutive patients after sarcoma resection from the proximal tibia and uncemented endoprosthetic reconstruction. At a mean final followup of 60 months (range, 9-152 months), there were no cases of aseptic loosening. Twelve (27%) patients suffered 14 complications leading to prosthetic failure due to infection (n = 7), stem fracture (n = 2), rotational instability (n = 1), vascular compromise (n = 2) and local tumor relapse (n = 2). However, limb salvage was successful in 37 of 44 (84%) patients. Functional assessment for 35 patients revealed a mean Toronto Extremity Salvage Score of 77/100 (range, 33-98) and Musculoskeletal Tumor Society 1987 and 1993 scores of 25/35 (range, 13-31) and 75/100 (range, 33-97), respectively. Mean knee joint flexion was 91 degrees (range, 0-110 degrees ) and knee extension lag was 6 degrees (range, 0-30 degrees ). Three patients with knee extensor complications had inferior functional outcomes. Aseptic loosening is uncommon with uncemented proximal tibia reconstruction, but decreasing other complications at this location remains challenging.

LEVEL OF EVIDENCE

Therapeutic study, level IV-1 (case series).

Uncemented tumor endoprostheses at the knee: root causes of failure

Although cemented tumor endoprostheses are the most commonly used method for reconstruction of the distal femur or proximal tibia after resection of primary bone tumors, aseptic loosening remains a common complication. Uncemented tumor prostheses may minimize this problem. We investigated the root causes of prosthetic failure for 99 patients with a fixed-hinge, bone-ingrowth Kotz Modular Femur and Tibia Resection System endoprosthesis and compared complications that led to implant failure with results in the literature. Of the 74 distal femoral implants and 25 proximal tibial implants, 25 patients had complications that resulted in prosthetic failure (removal of the prosthesis) at a median of 24.1 (range, 0.8-72.6) months. Failure was caused by prosthesis (n = 18) or oncologic-related (n = 7) complications. However, limb-salvage was possible for 87 of 99 patients. Smaller stem size in the distal femur and longer bone resection length in the proximal tibia were significantly associated with increased risk of prosthetic failure by multivariate analysis. The risk of stem fracture (6 of 99 patients) and infection (10 of 99 patients) was higher than other reports, but aseptic loosening (2 of 99 patients) was uncommon. These results suggest that although the bone-ingrowth surface of this prosthesis leads to a very low aseptic loosening rate, the higher risk of stem fracture and infection must be addressed in future implant designs.

LEVEL OF EVIDENCE

Therapeutic study, level IV-1 (case series).

Rehabilitation after total femur replacement: a report of 2 cases

We describe the rehabilitation of 2 patients who underwent total femur replacement after neoplastic involvement of the bone. In the past, patients with cancer of the femur were generally advised to undergo a hip disarticulation or transfemoral amputation. It is now feasible to salvage the limb in selected patients, by excising the entire femur together with any contiguous soft tissue tumor and replacing it with an endoprosthesis. The surgical literature contains a number of reports on total femur replacement, which mention the rehabilitation aspects only briefly, but we found nothing on this relatively uncommon form of surgery in the rehabilitation literature. Physiotherapy techniques such as active assisted exercises, isometric exercises, and hydrotherapy are extremely useful during the early phase of rehabilitation to facilitate a graduated strengthening program. Certain exercises, such as active hip abduction or knee flexion, may not be permitted for several weeks to protect muscles that have been reattached to the prosthesis. Partial weight bearing may be required to allow incorporation of bone allograft around the prosthetic hip joint. Because of these factors patients with total femur replacement may need a longer period of rehabilitation (6-8wk) than patients with total hip or knee replacement. Patients with total femur replacement can, however, achieve full independence with an appropriate rehabilitation program.

Functional evaluation in distal femoral endoprosthetic replacement for bone sarcoma

A multicenter study of successfully treated patients (mean age, 36.7 years) with a minimum 1-year followup (average, 35.4 months) after distal femoral endoprosthetic replacement for bone sarcoma was done using the 1987 and 1993 versions of the Musculoskeletal Tumor Society, the Short Form-36, and the Toronto Extremity Salvage Score functional evaluation criteria. Fifty-six patients (28 women and 28 men) fulfilled the criteria. Thirty-one Kotz prostheses (fixed hinge, uncemented) and 25 Modular Replacement System Prostheses (rotating hinge, cemented) were used. Thirty-five patients walked without aids, 19 used a cane, and two used crutches or a walker. The Musculoskeletal Tumor Society 1987 mean score was 28.1. The Musculoskeletal Tumor Society 1993 mean score was 80.4. The Toronto Extremity Salvage Score mean was 81.6. The Short Form-36 Physical Component Score had a mean of 43.2 and Mental Component Score mean of 54.2. The two groups of implants were comparable, except for the length of bone resection. Multivariate regression analysis revealed that patient age, existence of a pathologic fracture, and type of prosthesis all significantly accounted for differences in functional outcome as measured by the Musculoskeletal Tumor Society 1993, the Toronto Extremity Salvage Score, and the Short Form-36 Physical Component Score scales. Although both implants provided satisfactory function, the Musculoskeletal Tumor Society 1993 and the Toronto Extremity Salvage Score results were significantly better with the Modular Replacement System prosthesis. The effect of possible differences among surgeons or institutions was not addressed.

Functional and clinical outcomes of limb-sparing therapy for pediatric extremity sarcomas

PURPOSE

To determine the clinical and functional outcomes of children undergoing limb-sparing therapy for extremity sarcomas.

METHODS AND MATERIALS

We retrospectively reviewed 30 patients, age < or = 21 years, who were treated between l979 and l998 with external beam radiotherapy as a component of limb-sparing therapy for primary sarcomas of the extremity at UCSF. Included were patients for whom complete follow-up and functional outcome assessments were available. We assessed the patterns of failure, overall survival, disease-free survival, local control, and limb function.

RESULTS

At a median follow-up of 3 years, 12 of the 30 patients recurred: 3 locally, 8 distantly, and 1 with synchronous local and distant disease as site of first progression. Eighteen patients were alive with no evidence of disease. The median overall survival was 10 years, with a median disease-free survival of 8 years. Functional outcome assessment revealed 15 patients retained excellent, 12 good, 1 fair, and 2 poor limb function.

CONCLUSION

In pediatric patients receiving limb-sparing therapy, 90% maintained excellent or good limb function without compromising survival, demonstrating the validity of limb preservation in children with extremity sarcomas.

Outcomes after multi-modality treatment of musculoskeletal tumours

Outcomes of treatment of musculoskeletal tumours are evaluated for effectiveness of chemotherapy protocols, function obtained after surgery and survival after treatment. Quality of life achieved after multimodality treatment is dependent on a combination of all of these factors. Quality of life varies significantly along the treatment pathway, and continuously through the life of a patient. The patient's perception of outcome is based on the total effect of the disease and its treatment, rather than necessarily focussing on separate items of treatment. We have found that visual analogue scales can be used effectively to gauge the patient's perception of their quality of life. Such a method has shown that, overall, perceptions of quality of life seem to be better for those patients who have undergone successful limb salvage surgery when compared with those who have undergone amputation, but the differences are not as great as might be assumed.

Megaprostheses after resection of distal femoral tumors. A rotating hinge design in 30 patients followed for 2-7 years

Between 1981-1993, we inserted 32 Kinematic Rotating-Hinge Knee tumor prostheses in 30 patients, of which 2 concerned revisions of the same type of prosthesis. The diagnoses were 21 osteosarcomas, 2 chondrosarcomas, 2 Ewing's sarcomas, 2 metastatic breast carcinomas, 1 multiple myeloma, 1 giant cell tumor and 1 Gorham's disease. The median age was 25 (12-60) years and the median follow-up for survivors was 3.5 (2-6.6) years. There were 7 metastases and 1 local recurrence. 20 knees had excellent (MSTS) scores for motion (median flexion 120 degrees), 8 had good (84 degrees) and 4 had fair (45 degrees). The overall function was excellent in 6 cases, good in 14, fair in 9 and poor in 3. The radiographic assessment (ISOLS) gave "excellent" or "good" scores in 27 knees for bone remodelling, 31 for the interface, 28 for the anchorage, 31 for the implant body and 30 for the articulation. Extracortical bone bridging greater than 25% was observed in 18 of 27 prostheses.