Megaprosthesis

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Introduction

A tumour prosthesis (called sometimes a massive endoprosthesis or a megaprosthesis) is a specialised type of implant used in limb reconstruction surgery to replace a joint together with a large segment of bone. This technology is used after the resection of a tumour or infected bone or in trauma with extensive bone loss. Megaprosthesis allows to restoration of function and mobility in a patient with large bone defects, in case the biological reconstruction of bone and joint is not possible.

Indications and Contraindications

Megaprosthesis Indications

Megaprosthesis is typically indicated for severe bone defects too large or not amenable for other reconstructive techniques, it is used in the reconstruction of limb function after the following conditions:

Bone Tumour Resection: To ensure complete resection of the tumour, it needs to be removed together with a substantial margin of healthy tissue. This creates a massive bone defect and compromises adjacent joint integrity.
Massive Bone Loss from Injury: Substantial loss of bone and joints can result from high-energy trauma.
Chronic Bone Infections: Successful eradication of bone and joint infection often relies on wide resection of dead and infected bone. This produces an irreparable bone gap and joint loss.
Failed Previous Reconstructions: When previous limb reconstruction surgeries have not provided satisfactory solutions, with stable, durable and functional outcomes.
Patients with bone and joint loss, whose underlying medical conditions do not allow for a series of reconstructive surgeries.

Contraindications

While megaprosthesis is a reasonable solution, there are certain contraindications, including:

Poor General Health: Patients with significant medical conditions or on medication that increases the risks associated with anaesthesia and surgery.
Uncontrolled Infection: Any artificial joint and bone replacement is contraindicated in the settings of active infections.
Inadequate Soft Tissue Coverage: An adequate soft tissue envelope is a prerequisite to the successful implantation of an artificial joint and bone segment.
Unrealistic Expectations: Patients with unrealistic expectations about the outcomes of surgery may not be considered suitable candidates.

Benefits and Risks

The benefits and risks of megaprostheses are similar to general surgical risks and risks specific to the use of artificial implants, such as hip replacement and knee replacement.

The benefits and risks specific to megaprosthesis surgery are:

Benefits

Restoration of Function and limb stability: Megaprosthesis are designed to restore function and the ability to bear weight.
Improved Quality of Life: Significantly enhanced the quality of life often allowing to avoid amputation or severe disability.
Customisation: Megaprostheses can be made to fit each patient’s specific anatomical and functional requirements.
Reduced Pain: Helps alleviate chronic pain and discomfort that often accompanies conditions bone tumours or extensive bone trauma.
Longevity: Modern implants are durable, reducing the need for frequent surgical revisions.

Risks

Implant Failure: Although rare, revision surgeries may be required in case of implant failure.
Soft Tissue Complications: Soft tissue coverage may be compromised in large resections after tumours or extensive trauma.
Limited Range of Motion: a restoration of full, uncompromised function is rare due to the complex nature of underlying conditions
Nerve Damage: Extensive tissue preparation around the implant area can cause local nerve damage.
Bone Resorption: is common at the bone-implant interface, potentially compromising the stability of the implant.
Complications in Younger Patients: Megaprosthesis implants may need to be replaced due to the patient’s growth and implant wear.

Surgical Approach

A number megaprosthesis designs are used to address various bone and joint defects:

Segmental Megaprosthesis are used to replace a large section of a long bone, such as the femur or tibia, and often includes an adjacent joint replacement.
Modular Megaprosthesis can be customised from available components, to meet the surgical needs of the patient, based on the intraoperative needs.
Custom-made Megaprosthesis are employed in patients who cannot be fitted with a segmental or modular prosthesis, due to individual circumstances or complex defect’s morphology.

Two-stage procedures may be needed to eradicate severe bone infections or address significant deformity before the definitive surgery with megaprosthesis can be employed. Biological Reconstruction can be combined with megaprosthesis implantation where appropriate. Bone grafts, vascularised bone transfers, and bone allografts can be used to increase bone stock around megaprosthesis. Soft Tissue Reconstruction such as muscle flaps or skin grafts or tendon transfers may be performed to provide sufficient coverage and improve functional outcomes.

The choice of surgical option depends on the patient’s specific condition, the location and size of the bone defect, and the surgeon’s expertise. Megaprosthesis implantation requires meticulous planning, precise surgical technique, and thorough post-operative care to achieve optimal outcomes. Whenever possible a specialised megaimplant can replace an extensive bone segment loss, help restore the limb stability, function, and mobility and prevent the need of limb amputation.

Pre-Surgery Information

The following is what can be expected before a megaprosthesis procedure

Patient Evaluation: A thorough assessment of the patient’s overall health, medical history, and orthopaedic condition. When necessary, your health might need optimisation and we may refer you to another specialist.
Medications: Inform your healthcare provider about any medications you’re taking, as some may need to be adjusted before surgery. You should stop taking aspirin or anti-inflammatory medications 10 days prior to the surgery. Also, you should discontinue any naturopathic or herbal medications during this period.
Imaging: X-rays, CT scans, and MRIs are used to evaluate the extent of damage and plan the surgery. CT scans are especially helpful in planning the surgical steps.
Skin preparation: The night before and on the morning of the operation, you will be asked to wash the leg with a sponge provided at the pre-admission clinic. If there is any suspicion of an iodine allergy, a Betadine Skin test might be used.
Bowel Prep: Glycerin suppositories will be provided at the pre-admission clinic, and you will need to administer them the evening prior to the surgery. An instruction leaflet will be given to guide them.
Patient education: During a physiotherapy assessment, a qualified physical therapist will provide you with personalised instructions on gait training, the use of crutches, and pre- and postoperative exercises. You will be fitted with crutches to take home and practise before the surgery.

On the day of the Surgery

Surgical paperwork will be administered by the nurses, and the anaesthetist will meet with the patient to ask a few questions.
A hospital gown will be given, and the operation site will be shaved and cleaned.
Betadine skin prep will be applied to the area above the operation site and wrapped.
All x-rays are to be sent with the patient to the theatre.

Surgical Procedure

Anaesthesia: General anaesthesia or regional anaesthesia (spinal, epidural etc.) is used to ensure a pain-free procedure.
Incision: An incision will be determined by the nature of bone deficiency, soft tissue involvement and prosthesis used.
Bone and soft tissue resection: Morbid tissues will be meticulously removed.
Implant: An appropriate implant is inserted to restore the limb’s length, stability, alignment and joint function. Additional procedures may be needed to stabilise the bone around the implant. Anatomical alignment and stability of fixation are confirmed with x-rays.
Soft tissue coverage: may need to be guided by plastic surgeons.
Closure: The incision is closed using sutures. Dressing is applied and Vacum Assisted Wound Closure may be indicated in case of soft tissue compromise. Immobilisation may be indicated.

Post-Surgery Information

Hospital Stay: Segmental reconstruction with megaprosthesis is a serious surgery, you’ll typically be admitted into a hospital for several days to weeks for monitoring, and initial rehabilitation.
Pain Management: Pain medications will be administered to keep you comfortable.
Weight-Bearing: When necessary, you will remain non-weight-bearing for a period of time. Then you will commence weight-bearing gradually, with crutches, boots, or brace protection, following your surgeon’s instructions.
Follow-Up: Regular follow-up appointments with the team will help monitor your progress and address any concerns:

1 week postop: for wound check.
2 weeks postop: for sutures removal and x-rays.
6 weeks postop: for x-ray assessment and rehabilitation progress.
Later at 3, 6, 9, 12 months postop and further annually a follow-up with an x-ray will be mandatory.

Physical Therapy: A tailored rehabilitation program will help regain strength, flexibility, and mobility.
Lifestyle Adjustments: Patients need to modify their activities and household environment to accommodate for the lengthy bone reconstruction process, to ensure optimal healing and comfort.

Concerns

If patients are worried about their level of pain, experience significant bleeding, or notice fever or redness around the surgical site, they should contact the office immediately. If assistance is needed after hours, patients can contact the hospital where the surgery was performed, and they will contact Professor Al Muderis on their behalf.

Norwest Private Hospital: (02) 8882 8882

Macquarie University Hospital: (02) 9812 3000