Bassam A. Masri, M.D., FRCSC &
Peter L. Munk, M.D., FRCPC
Departments of Orthopaedics and Radiology, University of British Columbia, Vancouver, BC

Bone is a common site of hematogenous metastasis from carcinomas, with the prostate, lung, kidney, thyroid, breast and lung being the most common malignancies that metastasize to bone. The spine is the most common site of bony metastasis, with the lower limb being the second most common region of metastasis. The proximal ends of limbs are more commonly affected than the distal ends. Accordingly, the proximal femur and the proximal humerus are commonly affected sites. The upper extremity is not a common site of metastasis; however, when metastases occur in the upper extremity, there are special concerns that need to be taken into consideration, particularly when the metastases are in a subarticular location.

By virtue of the fact that the proximal ends of the limbs are more commonly affected than the distal ends, the proximal humerus is a common site of metastasis.

The surgeon has to consider several factors when dealing with metastases in the upper extremity:

1. The nature of the malignancy
2. Response to nonoperative modalities
3. The location of the tumour

The Nature of the Malignancy

One of the most important factors to note is the effect of the presence of the metastasis on the life expectancy of the patient, as well as its anticipated response to nonoperative treatment. The longer the course of the disease, the more aggressive the treatment should be.

While treating metastatic disease will not lengthen survival, in most cases, it will improve function.

Of the neoplasms that metastasize to bone, the tumour with the shortest average survival is metastatic lung carcinoma. These patients have a mean survival of less than a few months, and therefore, they are best treated medically, rather than surgically. Other diseases have a more indolent course, such as prostate carcinoma, and aggressive treatment is indicated.

Thyroid and renal cell carcinomas tend to cause a large amount of bleeding due to their vascularity. For this reason, trans-arterial selective embolization may be important to reduce blood loss when surgery is being considered.

Response to Nonoperative Modalities

Some tumours such as breast carcinoma and prostate carcinoma are very sensitive to radiotherapy. Therefore, unless the bone to be resected is disposable, every effort should be made to preserve the normal anatomy. Sometimes, the joint may be salvaged and the defect filled with bone cement, and the bone reinforced with a plate and screws. Clearly, if there is collapse in the subarticular bone, then radiotherapy alone would not be effective, and a reconstruction of the joint, with a regular joint replacement prosthesis, or with an oncology implant would be required.

Renal cell carcinoma and thyroid carcinoma tend to bleed excessively if entered at the time of surgery. For this reason, I would recommend preoperative embolization of the lesion to minimize blood loss. Alternatively, if the lesion is unresectable or the patient is too unwell for surgery, then embolization alone could be used for palliation with some reports of lasting benefit.

Location of the Tumour

The specific management of a tumour not only depends on the type of tumour, but also on its specific location within the upper extremity. In general, subarticular tumours need reconstruction rather than prophylactic fixation, unlike diaphyseal tumours. Certain joints, such as the shoulder joint, lend themselves more to reconstruction by virtue of the available techniques. The proximal humerus is a common site of primary malignancies of bone, and therefore, a variety of techniques exist for reconstruction after resection. Other joints, such as the elbow, are less commonly affected by primary bone tumours, and therefore reconstructive techniques are not as well developed.

Metastases that affect the clavicle, for the most part, require radiotherapy alone. However, if there is sufficient bone destruction that radiotherapy alone is not sufficient to control the symptoms, then resection of the end of the clavicle (particularly the distal end) is possible. This is particularly true for metastatic renal cell carcinoma due to the poor response to radiotherapy.

The scapula is more difficult to deal with because of its location. Tumours that affect the glenoid are more difficult to treat, and radiotherapy alone is often sufficient for most tumours. In the case of metastatic renal cell carcinoma, if the symptoms are not palliated with embolization, repeat angiography with repeat embolization and resection of the glenoid with suspension of the humerus from a rib can be performed. With this procedure, shoulder function is poor, although more distal function is well preserved.

The proximal humerus is a common site of metastasis from carcinoma. In small lesions with collapse, a shoulder hemiarthroplasty is sufficient. Due to loss of proximal bone stock, cemented fixation is preferred with reconstruction of the tuberosities onto the suture holes in the femoral component. This procedure is not unlike a shoulder hemiarthroplasty for a three or four-part fracture of the proximal humerus. Long-stem implants should also be available in case of other metastatic lesions farther distally within the humerus. If the lesion is more extensive, and a standard or long-stem shoulder hemiarthroplasty is not possible, the proximal humerus should be resected. For primary bone sarcomas, the reconstruction depends on the activity level of the patient. For the more active laborer, a shoulder arthrodesis with an intercalary allograft gives better function. In the more sedentary patient, replacement of the proximal humerus with a modular prosthesis is more predictable, although the function is not as good as with an arthrodesis. The implant functions as a spacer, and shoulder function is poor. In the case of metastatic disease, a modular prosthesis is the reconstructive technique of choice, because of the more predictable result, fewer potential complications and faster rehabilitation. Occasionally, for small lesions, internal fixation along with cement augmentation can be used. The proximal humeral blade plate is a useful device for these lesions, as long as there is sufficient bone stock within the humeral head to support the plate, and as long as the tumour is radiation-sensitive.

Lesions of the distal humerus (particularly if extensive) are more difficult to treat. Metastatic renal cell lesions can be treated with embolization. If embolization is not effective, then resection of the distal humerus is required. A distal humerus replacement can be used for the reconstruction of the skeletal defect. Other types of metastases can be treated with radiation therapy. If the lesion is so extensive that reconstruction is necessary, the surgeon can use internal fixation with bone cement augmentation, coupled with postoperative radiotherapy or an elbow replacement, followed by radiotherapy.

Lesions in the ulna and radius are even less common. Lesions in the olecranon can be treated with prophylactic fixation and cement augmentation, if the lesion is too extensive for radiotherapy alone. Lesions in the proximal radius are best treated with radiotherapy alone, as the proximal radius is not critical for the functioning of the forearm. Likewise, the distal ulna is not critical for the functioning of the forearm and can be treated with radiation or resection, depending on the type and extent of the tumour. Lesions of the distal radius are extremely uncommon. If internal fixation with cement augmentation is not possible, then resection and reconstruction is required. Many reconstructive techniques are possible. These include a wrist fusion with autogenous non-vascularized or vascularized fibula. Considering the limited life expectancy of these patients, the risks and morbidity of a vascularized fibular transfer may not be warranted. Other techniques include wrist fusion with intercalary allograft, as well as transferring the distal ulna to the radius to achieve a fusion. Finally, a wrist fusion between the ulna and the carpus can be performed, however, this leads to a one-bone forearm, and pronation and supination will be lost.

Lesions in the hand require resection or amputation for the most part. The hand is a difficult organ to irradiate.

In summary, periarticular metastases of the upper extremity are not as common as other metastases, yet they can be devastating. A variety of nonoperative and operative techniques exist for minimizing the patients' agony, while allowing them independent function for the longest possible amount of time.

Renal Cell Metastasis to Proximal Humerus

a) Coronal fat suppressed inversion recovery image (TR 5000 TEef 15 TI 150) of the proximal humerus depicts a large destructive lesion replacing the humeral head and the proximal diaphysis.

b) Arterial phase image from the angiogram shows an intensely vascular tumour with pronounced tumour staining and neovascularity.

c) Embolization catheter in position prior to delivering particle emboli. The destructive nature of the tumour is apparent