Evaluation of tumor-prostheses over time: Complications, functional outcome, and comparative statistical analysis after resection and reconstruction in orthopedic oncologic conditions in the lower extremities

Validity of the Musculoskeletal Tumor Society Score for lower extremity in patients with bone sarcoma or giant cell tumour of bone undergoing bone resection and reconstruction surgery in hip and knee

BACKGROUND

The Musculoskeletal Tumor Society Score (MSTS) is widely used to evaluate functioning following surgery for bone and soft-tissue sarcoma. However, concerns have been raised about its content validity due to the lack of patient involvement during item development. Additionally, literature reports inconsistent results regarding data quality and structural validity. This study aimed to evaluate content, structural and construct validity of the Danish version of the MSTS for lower extremity (MSTS-LE).

METHODS

The study included patients from three complete cohorts (n = 87) with bone sarcoma or giant cell tumour of bone who underwent bone resection and reconstruction surgery in hip and knee. Content validity was evaluated by linking MSTS items to frameworks of functioning, core outcome sets and semi-structured interviews. Data quality, internal consistency and factor analysis were used to assess the underlying structure of the MSTS. Construct validity was based on predefined hypotheses of correlation between the MSTS and concurrent measurements.

RESULTS

Content validity analysis revealed concerns regarding the MSTS. The MSTS did not sufficiently cover patient-important functions, the item Emotional acceptance could not be linked to the framework of functioning, the items Pain and Emotional acceptance pertained to domains beyond functioning and items' response options did not match items. A two-factor solution emerged, with the items Pain and Emotional acceptance loading highly on a second factor distinct from functioning. Internal consistency and construct validity showed values below accepted levels.

CONCLUSION

The Danish MSTS-LE demonstrated inadequate content validity, internal consistency, and construct validity. In addition, our analyses did not support unidimensionality of the MSTS. Consequently, the MSTS-LE is not a simple reflection of the construct of functioning and the interpretation of a sum score is problematic. Clinicians and researcher should exercise caution when relying solely on MSTS scores for assessing lower extremity function. Alternative outcome measurements of functioning should be considered for the evaluation of postoperative function in this patient group.

Risk factors for peri-megaprosthetic joint infections in tumor surgery: A systematic review

BACKGROUND

Peri-megaprosthetic joint infections (PJI) in tumor surgery are complex and challenging complications that significantly impact the outcomes of the patients. The occurrence of PJI poses a substantial threat to the success of these operations. This review aims to identify and summarize the risk factors associated with PJI in tumor surgery with megaprosthetic reconstruction as well as to determine the overall risk of PJI in limb salvage surgery.

METHODS

A thorough examination of published literature, scrutinizing the incidence of PJI in tumor prostheses after limb salvage surgery was done. Research studies that documented the incidence of PJI in tumor patients who underwent limb salvage surgery, and explored the risk factors associated with the occurrence of PJI were deemed eligible.

RESULTS

A total of 15 studies were included in the analysis and underwent comprehensive examination. After the exploration of key parameters, several significant risk factors for PJI concerning the type of implant coating, surgical site characteristics, patient demographics, and procedural factors were recorded.

DISCUSSION

The findings underscore the need for a nuanced approach in managing tumor patients undergoing limb salvage surgery and megaprosthetic reconstruction, with emphasis on individualized risk assessments and individualized preventive strategies.

Influence of different fixation modes on biomechanical conduction of 3D printed prostheses for treating critical diaphyseal defects of lower limbs: A finite element study

Background

Applying 3D printed prostheses to repair diaphyseal defects of lower limbs has been clinically conducted in orthopedics. However, there is still no unified reference standard for which the prosthesis design and fixation mode are more conducive to appropriate biomechanical conduction.

Methods

We built five different types of prosthesis designs and fixation modes, from Mode I to Mode V. Finite element analysis (FEA) was used to study and compare the mechanical environments of overall bone-prosthesis structure, and the maximum stress concentration were recorded. Additionally, by comparing the maximum von Mises stress of bone, intramedullary (IM) nail, screw, and prosthesis with their intrinsic yield strength, the risk of fixation failure was further clarified.

Results

In the modes in which the prosthesis was fixed by an interlocking IM nail (Mode I and Mode IV), the stress mainly concentrated at the distal bone-prosthesis interface and the middle-distal region of nail. When a prosthesis with integrally printed IM nail and lateral wings was implanted (Mode II), the stress mainly concentrated at the bone-prosthesis junctional region. For cases with partially lateral defects, the prosthesis with integrally printed wings mainly played a role in reconstructing the structural integrity of bone, but had a weak role in sharing the stress conduction (Mode V). The maximum von Mises stress of both the proximal and distal tibia appeared in Mode III, which were 18.5 and 47.1 MPa. The maximum peak stress shared by the prosthesis, screws and IM nails appeared in Mode II, III and I, which were 51.8, 87.2, and 101.8 MPa, respectively. These peak stresses were all lower than the yield strength of the materials themselves. Thus, the bending and breakage of both bone and implants were unlikely to happen.

Conclusion

For the application of 3D printed prostheses to repair diaphyseal defects, different fixation modes will lead to the change of biomechanical environment. Interlocking IM nail fixation is beneficial to uniform stress conduction, and conducive to new bone regeneration in the view of biomechanical point. All five modes we established have reliable biomechanical safety.