Results of the treatment of bone metastases with modular prosthetic replacement—analysis of 67 patients

Conventional osteosynthesis (fixation with an intramedullary nail or plates with or
without bone cement) have represented a common option for surgical management of metastatic
lesions 9]–11]. Another possible choice of treatment that has been increasingly used is modular
prostheses due to possibly long survival time in patients with myeloma and other metastatic
cancers (breast, prostate, kidney, bowel, or thyroid cancer) 12]–17].

With the progress in oncology, a significant number of malignant cancers, particularly
those metastasizing to bones, have become chronic 18]–21]. Technological developments in other fields, including material science, anesthesiology
and surgical techniques, have made it possible to use large prostheses with an acceptable
risk of complications. Materials used in a manufacturing process are increasingly
better and biocompatible; therefore, the incidence of allergic reactions and intolerance
symptoms has been lower. The comparisons of various surgical treatment options, osteosynthesis
(with or without PMMA) and the prosthesis implantation, clearly indicate the superiority
of the latter as presented in literature (Fig 5) 18], 20], 21].

Fig. 5. Failed fixation (gamma nail with PMMA) of a proximal femoral fracture due to breast
cancer metastasis (a) and radiographs after modular endoprosthesis replacement (b)

The survival rate of the patients with modular prostheses after radical resections
of metastatic tumors is higher when compared to the patients that underwent outdated
standard treatment. The overall survival rate is sometimes as high as 37 months, which
obviously varies in different cases, depending on the type of cancer, the grade of
malignancy, the stage of the disease, and the methods of treatment 19]–22].

Most studies have found that treatment results are better in cases where pathological
fractures have never occurred which result from an easier technique of resection and
a lower incidence of recurrences. Thus, it is recommended to perform a surgery in
all the cases where metastases posing a risk of fracture were diagnosed. Clinical
and radiological criteria for determining the risk of pathological fracture are now
widely known. It should be kept in mind that a particularly high risk is associated
with bones subject to heavy loading (the femur, the tibia, and the vertebral column)
18], 21], 23]. The recurrence rate in patients after long-bone metastatic tumor resections ranges
from 4 to 28 %. The most important objective seems to be a wide margin with a cuff
of healthy tissues which is a condition necessary for effective treatment 6], 8], 21], 22], 24].

One should consider the possibilities of adjuvant treatment, especially the use of
radiation therapy and bisphosphonates. In the past, radiotherapy was a method of choice
in treating bone metastases, particularly to the spine and the pelvis. Currently it
is important as a method of reducing pain in 50–85 % of patients as well as reducing
the incidence of local recurrences after surgeries. Bisphosphonates are also effective
in pain reduction, and they significantly reduce the number of pathological fractures
by 25–50 %. They are particularly often used in the treatment of metastatic breast
cancer, prostate cancer, and multiple myeloma) 4], 6], 7], 25].

In the case of the metastases of kidney cancer, thyroid cancer, and myeloma, a trans-arterial
embolization (TAE) can be performed. This procedure limits vascularization of the
tumor, which results in a twofold or even threefold reduction in bleeding during the
surgery, and the operation time is reduced by about 25 %. Many authors have confirmed
the effectiveness of this treatment method in reducing pain and number of local recurrences
after resection of the tumor. Reduced intraoperative bleeding allows for more precise
preparation of tissues and resection of lesions. According to some authors, embolization
increases the sensitivity of tumor cells to chemotherapy and radiation therapy. We
have not performed preoperative embolization of tumors localized in the extremities
at our department. This procedure has been performed exclusively when the tumor was
localized in the pelvis and the spine 26]–28].

The indications for amputation due to cancer metastases are extremely rare. It is
performed in the case of large metastatic tumors infiltrating the vascular and nerve
trunks or skin when limb-salvage treatment is not possible. An indication for amputation
may be extensive inflammation of bone and soft tissues that is localized within the
site of a former prosthetic implantation and which is impossible to treat 2], 3], 18].

The present study clearly indicates that most metastases occur in the proximal area
of the femur. Metastases in other sites are less frequent; very rarely do they occur
in the area below the elbow or knee joint. Breast cancer is the most metastatic (Fig
6). Prostate cancer metastases, frequent as they are, rarely necessitate surgical treatment
because of a relatively low risk of a fracture.

Fig. 6. Radiographs of proximal humerus destruction by metastatic breast cancer (a) and after modular endoprosthetic replacement (b)

Most common complications that may follow modular alloplasty are surgical wound infections
29], 30]. Patients constitute a group at the highest risk of infectious and thromboembolic
complications because the surgeries are most often urgent, therefore, MRSA screening
or other pathogen detection tests are rarely carried out. There are no clear recommendations
as to the routine local antibiotic therapy in the case of primary resection alloplasty.
A rate of infectious complications ranges between 1.2 and 19.5 %. Preoperative radiotherapy
is seen as one of the major risk factors for developing infections. Major risk factors
include: decreased immunity as a result of neoplastic disease and chemotherapy, wide
surgical approach with significant blood loss, and the size of metal implants. Worse
still, the patients are usually elderly and with various general health problems.

Other potential complications include dislocation or loosening of the implants and
periprosthetic fractures. Revision procedures are required in 3–17 % of patients 31], 32].

The procedures concerning preparation and implantation of GMRS and MUTARS prostheses
differ. The MUTARS prostheses allow for a smooth rotation of the prosthesis stem.
What is more, surgical management of the bone marrow canal is carried out not by reaming,
but by rasping. The stems are bent, which minimizes the risk of damaging the cortical
bone while driving them. The prostheses have a golden and silver coating, which reduces
the incidence of infectious complications and allergic reactions.

Functional results of modular alloplasty are satisfactory, especially in patients
after proximal and distal femur resections. Decreased gluteal muscles function was
not a big problem to patients. Most of the patients walk efficiently without crutches.
A slight limb length discrepancy was not noticed by the patients and did not affect
their walking. The quality of life of the patients after metastasis resections and
implantations of modular prostheses improved significantly. The VAS and Karnofsky
scales showed clearly reduced pain and improved functioning.