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Hindquarter amputation (for pelvic soft tissue sarcoma)

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Soft-tissue tumours (STT) are a heterogeneous group of benign and malignant diseases accounting for fewer than 4% of all tumours in adults and fewer than 8% of all tumours in children. More specifically soft-tissue sarcomas are rare malignant tumours derived from mesenchymal cells at all body sites. These rare tumours comprise approximately 1% of all newly diagnosed cancers. The incidence of soft tissue tumours is approximately 2000 cases per annum in the UK.
Patients may present with a painful or painless swelling that is growing insidiously. Almost 50% arise in the lower limbs (most commonly the adductor compartment of the thigh) and the median age for presentation is 65 years. Concern as to the biological activity of a lesion should arise if the size is greater than 5cm, it is painful, deep to fascia, increasing in size, or represents recurrence of a previously excised lesion. Each of these five characteristics corresponds to an approximately 20% risk of malignancy. Any lesion presenting with features that are suggestive of STT require referral to specialist centres, where appropriate evaluation and staging will take place.
Bone involvement by such tumours is rare except in advanced disease or in aggressive, rapidly enlarging tumours where the tumour invades all surrounding structures including bone. In such cases, surgical resection must include the involved bone to ensure complete removal of the tumour. In rare circumstances, this requires amputation where the risk of local recurrence is deemed too high by limb salvage surgery, or where the function of the limb would be unacceptable.

INDICATIONS
Theodor Bilroth is credited with having undertaken the first hindquarter amputation in 1891. The patient died shortly after completion of the procedure from ‘shock’. Hogarth-Pringle was the first British surgeon to be credited with performing a successful hindquarter amputation, in 1900, on a ten-year-old girl with tuberculosis of the hip. She survived for 14 years. Hindquarter amputation has been regarded as a somewhat outdated procedure, particularly for high grade sarcomas of the pelvis, due to the poor prognosis for such tumour types. The increasing sophistication of imaging and methods of treatment of bone and soft-tissue sarcomas have reduced the need for hindquarter amputation by increasing the feasibility and frequency of limb salvage surgery. Despite this, it is still indicated either as primary treatment for large tumours that would otherwise be unresectable or following failure of previous salvage surgery, usually with local recurrence.
The indications for hindquarter amputation therefore, are either for disease cure where limb salvage surgery would compromise oncological outcomes, or for palliation in the presence of metastatic disease to improve pain and quality of life. More recently, hindquarter amputation has been used as treatment for failed limb salvage surgery, particularly pelvic reconstruction, in the presence of infection.
A variety of flaps have been described, depending on the residual blood supply after resection and where the tumour was located. The most common is the posterior flap based on gluteus maximus supplied by the superior gluteal pedicle. An alternative is an anterior thigh flap based on the femoral vessels . Rarely an adductor flap based on the obturator vessels is required where the superior gluteal pedicle and femoral vessels are involved by the tumour.

SYMPTOMS & EXAMINATION
A common early symptom is pain which often follows an insidious, intractable course from functional pain, to rest pain and finally night pain. Due to the rarity of the diagnosis, patients are often falsely reassured or under investigated, at least at the initial stages of the disease. Due to the distensibility of the pelvic cavity, tumours can reach a large size before a mass becomes palpable. The presence of a mass often stimulates further investigation. Patients rarely present with systemic symptoms of fevers, night sweats or weight loss except in advanced disease. Examination findings in patients with pelvic tumours are often non-specific. Acetabular involvement will often result in a limp and an irritable range of movements. Abdominal examination often demonstrates a mass in close association with the pelvis. The mass is often firm, irregular and heterogenous in texture, and fixed to underlying structures. Examination of the local lymph node structures occasionally reveals lymphadenopathy though this a rare feature. A full neurological examination should be completed as tumours will often compress neurological structures, or invade directly into the sacrum. The lower limb vascularity, both venous and arterial should be assessed looking in particular for the presence of vascular insufficiency or venous engorgement suggestive of pelvic vessels compression.
IMAGING
Radiographs should form the first line investigation for any suspected pelvic sarcoma and often these will identify areas of lysis suggestive of infiltration. In the case of pelvic soft tissue sarcomas, often the radiograph will appear normal. Cross sectional imaging for local staging should comprise an MRI scan, including the entire pelvis and sacrum, as well as proximal femora.
Tumours will appear as an enlarged high signal mass with soft tissue extension and in the case of tumours invading bone, lysis, destruction and oedema within osseous structures. Full staging should be completed before discussing management. In the case of soft tissue sarcomas, this should comprise CT scanning of the chest with addition of the abdomen and pelvis in certain tumour types. Whole body imaging is often not indicated for soft tissue sarcomas except for certain histological variants (eg myxoid liposarcoma). This may comprise whole body MRI or whole body PET-CT scan.
ALTERNATIVE OPERATIVE TREATMENT
Limb salvage is always the aim of surgical treatment at the outset. The principles of surgical management should be to remove the tumour in its entirety, with a clear margin with a degree of function post operation that is acceptable to the patient. Where this is not achievable with limb salvage, an amputation should be considered. In the case of pelvic sarcoma surgery the indications for hindquarter amputation are involvement of two of the following: the hip joint, sciatic nerve or femoral vessels. This may be offered after the administration of neo-adjuvant radiotherapy which would be aimed at arresting tumour growth, reducing the risk of local recurrence, or rarely to downstage disease and allow limb salvage surgery. In advanced disease, hindquarter amputation may still be offered to palliate particularly in the presence of intractable pain.
NON-OPERATIVE MANAGEMENT
Non-operative management may be considered in the presence of advanced metastatic disease, or where hindquarter amputation is not acceptable for the patient. In such cases, the patient may receive radiotherapy with palliative intent.
CONTRAINDICATIONS
Contraindications to hindquarter amputation are patient related, where the procedure is not acceptable to the patient, or surgical related, where the risk of peri-operative mortality is deemed too high to undertake the procedure.

The patient, a 68 year old gentleman, presented with an 8 month history of progressive pain affecting the right hip with neuropathic pain into the right leg. At presentation, he was unable to weight bear to pain. Local staging demonstrated a large tumour of the right iliacus with erosion of the ilium and extension into the sciatic notch to involve the buttock compartment.
Staging investigations demonstrated no evidence of metastatic disease.
Biopsy of the mass demonstrated features consistent with a high grade undifferentiated soft tissue sarcoma.
Given the extent of the localised tumour, the patient was counselled towards a hindquarter amputation with curative intent.
Following full, informed consent, the patient is anaesthetised. A combined spinal/epidural anaesthetic is often used to allow adequate post operative analgesia. Intravenous antibiotics are given prior to skin incision in line with the hospital policies. A urinary catheter is inserted to allow close monitoring of urine output post op. The patient is positioned in a floppy lateral position with the leg free-draped to allow manipulation during the amputation. Drapes are applied to the midline anteriorly and below the midline of the sacrum posteriorly. A betadine soaked pack is placed in the rectum which is covered but allowed to be exposed at the end of the procedure to ensure there has been no rectal injury. The procedure is undertaken in a laminer flow theatre. A WHO check list is completed before starting the procedure.

Axial T2 weighted MRI scan showing a large heterogenous mass occupying the entire buttock compartment extending through the sciatic notch. The external iliac vessels can be seen anteriorly free of tumour.

Axial MRI scan demonstrating the plane of the posterior osteotomy through the midline of the sacrum exiting laterally anteriorly medial to the visible tumour.

Anteriorly the osteotomy extends through the superior pubic ramus lateral to the midline where the ramus can be easily identified.

The inferior pubic osteotomy extends through iscium using the obturator membrane as a landmark below the level of the tumour. Therefore, the leg and pelvis will be removed retaining a small portion of the superior pubic ramus and the majority of the inferior pubic ramus.

The skin markings for incision are marked carefully before commencing. The posterior extent of the flap extends around the anal margin to ensure the buttock is excised with the tumour.

The distal extent of the flap incorporating the anterior compartment of the thigh is marked out before incision.

The initial skin incision starts at the pelvis to mobilise the vessels and ensure they are clear of the tumour.

The incision begins above the anterior superior iliac spine and through the abdominal wall in line with a utilitarian approach to the pelvis. The skin, subcutaneous fat and overlying fascia of the anterior abdominal wall is divided.

The abdominal wall (A) is divided away from the ilium.

The reroperitoneal space is opened by reflecting the abdominal wall from the ilium leaving the iliacus fascia over iliacus and the underlying tumour.

Having entered the retroperitoneal space, the muscles arising from the anterior superior iliac spine can be reflected off the front of the ilium.

Having mobilised the hip flexors and connecting to the retroperitoneal approach, the vessels can be visualised.

At this stage, the internal iliac (A) can be mobilised from the common iliac artery. As this will be sacrificed with the tumour this can be tied and divided.

Axial MRI demonstrating the anatomy of the common iliac artery at the level of the bifurcation highlighting the underlying iliacus fascia which forms a barrier between the vessel and the underlying tumour. The internal iliac artery needs to mobilised to allow its division proximal to the sciatic notch which is involved by tumour.

The internal iliac artery is tied with vicryl ties and divided.

The external iliac artery (A) can now be mobilised down to the inguinal ligament and anterior thigh whilst the internal iliac artery (B) is tied.

The common iliac vein (A) can now be mobilised and the internal iliac vein visualised.

The external iliac vein can now be mobilised distally into the anterior thigh whilst the internal iliac vein (B) is tied with vicryl ties. The femoral nerve (C) can be seen lying between iliacus and psoas.

Having mobilised the femoral vessels, and tied the internal iliac vessels, the anterior thigh flap can be prepared. The pre marked incision os opened distally above the knee.

The skin, subcutaneous fat and fascia lata/ilio-tibial band can be divided over the lateral distal thigh.

The deep fascia is sutured to the underlying muscle to prevent the overlying skin and subcutaneous tissue from being inadvertently pulled away (A). The quadriceps tendon (B) can now be divided proximal to the patella.

The quadriceps can now be elevated off the femur (A). The suprapatellar pouch (B) remains attached to the distal femur and knee.

The quadriceps is reflected from distal to proximal off the underlying femur.

The entire quadriceps (A) is elevated laterally to join with the previous anterior dissection at the pelvis. The previous dissection has mobilised the sartorius and tensor fascia lata off the anterior superior iliac spine whilst the underlying rectus has been reflected off the anterior inferior iliac spine. B: Femur. C: Divided quadriceps tendon.

Attention can now be turned to the medial distal dissection of the thigh. The quadriceps compartment is elevated off the interosseous membrane distally which is divided to expose the femoral vessels (A) beneath. The interosseous membrane is easily identified as a thick band of fascia once the quadriceps compartment has been elevated. A window is created in the membrane away from the femur to prevent inadvertent injury to the vessels beneath. This allows an artery clip to be passed beneath the fascia and its division extending medially to gain access to the vessels.

The femoral vessels are mobilised, tied and divided. Using a pair of DeBakey forceps and a Lahey the vessels are mobilised utilising the perivasular plane. Once a short section of the artery and then the vein have been mobilised, 2 artery clips can be used to cross clamp the vessels. The vessel can then be divided and the ends tied using 2/0 vicryl sutures, with 2 ties on the retained vessel stump.

Having divided the femoral vessels distally the quadriceps compartment can be mobilised off the femur and the interosseous membrane, as previously described for the lateral dissection. The dissection can be extended proximally up to the level of the profunda femoris which needs to be mobilised and ligated. Again, this is best done by mobilising a short section of the vessel, cross clamping and double tying with vicryl sutures.

Having divided the profunda, the entire quadriceps is now mobile up to the pelvis margin.

At the pelvic margin, the quadriceps compartment can be mobilised medially to expose the superior pubic ramus (A). The level of the anterior osteotomy can be marked at this level. The quadriceps compartment with the femoral vessels (B) is seen lying anteriorly.

Attention can now be turned to the posterior dissection. The skin, subcutaneous fat and deep fascia are incised over the pelvic margin. The erector spinae muscles are mobilised off the pelvic brim to expose the ilum and lateral process of L5. At this level, the ilio-lumber venous plexus is seen and divided.

The posterior dissection extends around the pelvic brim extending medially to the midline of the sacrum. The skin, subcutaneous fat and deep fascia are divided and the midline identified.

The dissection continues distally down to the tip of the coccyx. Lateral to the tip of the coccyx, the soft tissues can be divided reflecting the anal suspensory ligaments off the tip of the coccyx and the fascia from the lateral border of the coccyx.

At this stage the medial dissection of the adductor compartment can be completed dividing the adductors distal to their origin. The dissection continues laterally and posteriorly directed towards the ischium. As the hamstring origin is to be removed with the tumour, the sacrotuberous ligament can be left in continuity.

The medial and posterior dissections are connected by dividing the tissue overlying the ischio-rectal fossa. The rectum will therefore lie medially away from the inferior pubic ramus osteotomy.

At this stage, the anterior osteotomy can now be completed through the superior pubic ramus. The obturator membrane can safely be divided at this level. Obturator internus and externus have already been divided medially. An artery clip or Lahey can be passed around the ramus and the bone divided using an osteotome or Gigl saw.

The ischio-rectal fossa can be identified and a finger passed in front of the ischium to protect the rectum. The bone can be divided medial to the hamstring origin and distal to the tumour using an osteotome.

The ischium is now divided with an osteotome.

Now that the ischium has been divided, the osteotomy through the sacrum can begin. A finger is passed into the inside of the pelvis from distally and the osteotome directed with the surgeons free hand. The surgeon can then direct the osteotome towards their finger which is placed away from the palpable tumour margin. The assistant is then responsible for driving the osteotome forward whilst the surgeon directs the osteotome until the tip is palpable on the inside finger.

The osteotomy passes from distal to proximal using a raft of osteotomes.

Proximally, the osteotomy is completed through the sacrum. The osteotomes can be left in place and used to gently lever the pelvis forward to complete the osteotomy in a controlled manner.

The final soft tissue attachements are now divided to complete the amputation. Proximally, this will involve dividing the psoas proximally to the pelvic brim. Distally, the pelvic floor can be divided away from the pelvis.

Having completed the amputation, the external iliac vessels (A) can be seen supplying the anterior thigh flap (B). The divided sacrum (C) can be seen posteriorly.

The resection specimen showing the filleted femur (A) and the medial extent of the pelvic tumour (B).

The medial edge of the tumour (A) can be seen at the proximal end of the amputation. The divided sacrum (B) can be seen proximal to the tumour.

The anterior thigh flap is now rolled over the defect with the distal end of the flap coming to appose the posterior dissection over the divided sacrum.

The wound over the pelvis can now be closed. The abdominal wall is reattached to the deep fascia of the flap, The repair uses vicryl over 2 suction drains. Further layered closure is with vicryl. The skin is closed using clips or subcutaneous absorbable sutures. A vacuum assisted dressing is applied over the wound only and low negative pressure applied.

The final repair using the anterior thigh flap.
The flap is covered with VAC dressing on low pressure. The drains are released after 20 minutes.

Post operative radiograph showing the levels of the osteotomies through the lateral sacrum and the superior and inferior pubic rami anteriorly.

The patient is nursed on a high dependancy unit.
The VAC remains in situ for 5 days and the wound is then reviewed.
Antibiotics are continued for 5 days, usually vancomycin and meropenem.
The drains remain in situ for 5 days or until <100ml drainage per 24 hours.
The patient remains on bed rest until the wound is reviewed at 5 days.
Following discharge, the resection specimen is reviewed by a specialist musculoskeletal pathologist and the case reviewed by the sarcoma multidisciplinary team. The follow up protocol is as per established guidelines. The patient is seen at 3 monthly intervals for the first 2 years with chest x-ray and examination, 6 monthly until 5 years and annually thereafter.

The outcomes following hindquarter amputation have evolved in line with advances in multimodal oncology management. Early reports suggested a dismal outcome following the procedure. Masterson et al (Masterson et al CORR,1998;350:187– 194) reported on 14 cases of hindquarter amputation for high grade pelvic sarcoma, 13 of whom developed metastases, 12 of whom died. In the most comprehensive series to date, however, Grimer et al reported the outcomes from a consecutive series of 157 hindquarter amputations (Grimer et al, BJJ,2013;95-B:127–31.). The early mortality was 1.3% at 30 days.Infection remained a problem but in most cases this was managed conservatively, only occasionally requiring return to theatre for washout and debridement.
Local recurrence occurred in 23 patients (15%) at a mean of 2.3 years. This was largely dependant on the margin achieved at amputation, and the histological type. In many of the local recurrences, metastases occurred synchronous to the recurrence or very shortly thereafter. In a small proportion of these recurrences, the recurrence was excised and a small subset of patients remain alive.
The overall 5 and 10 year survival was 45% and 36% respectively. This was affected by the tumour grade and type with high grade tumours having a 5 year survival of 41% whilst low grade chondrosarcomas had a a 73% 5 year survival.
The evolution in anaesthetic, imaging and oncology management for patients with advanced pelvic sarcoma is ongoing. However, in the absence of revolutionary curative treatments, there remains a role for aggressive, disfiguring and mutilating procedures such as hindquarter amputation. In selected patients, the procedure remains a viable if the only, option for cure of pelvic sarcoma.


Reference

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