The medial head gastrocnemius muscle transposition flap for coverage and functional restoration in limb-salvage surgery of bone tumors in the proximal tibia

The medial head gastrocnemius muscle transposition flap for coverage and functional restoration in limb-salvage surgery of bone tumors in the proximal tibia

Mohamed Abdel Rahman,a MD; Salah Nasser,b MD; Ikram Safe,b MD

a) Department of Orthopedic surgery, Ain Shams University, Cairo, Egypt.

b) Department of  Plastic and Reconstructive Surgery, Ain Shams University, Cairo, Egypt.

Abstract

Introduction: Limb-salvage surgery has become the standard mode for treatment of the proximal tibia tumors. Its goals are complete eradication of the tumor with minimal complications, while maintaining acceptable functional, durability and cosmetic appearance of the limb. The most serious problem encountered after tumor resection and skeletal reconstruction by endoprosthesis or bone grafts is the lack of enough soft tissue coverage, which is the direct cause of delayed wound healing, exposure of prosthesis and infection. Another difficult aspect is the need for reconstruction of the extirpated extensor mechanism. In the present study the medial head gastrocnemius muscle flap was used to reconstruct the defect, cover the prosthesis and / or the fibular graft, as well as to reconstruct the extensor mechanism. Both the clinical outcome and functional results will be presented.

Patients and methods: Sixteen patients (8 males and 8 females), with a mean age of 24.4 years (range 13-58 years) at time of surgery, were included in this work. According to the staging system of Enneking et al, they were 4 patients with an aggressive giant cell tumor (25%), and 12 patients with primary malignant bone tumors (75%) of the proximal tibia. One of the

12 patients was grade I B and the other 11 were grade II B. Wide resection was performed in all the patients followed by reconstruction by modular replacement endoprosthetic system in

10 patients, pedicled fibular transfer and knee fusion in three patients, and non-vascularized fibula graft with knee fusion in three patients. In all the 16 patients a medial head gastrocnemius transposition muscle flap was used for coverage and to reconstruct the extensor mechanism. The   follow   up   ranged   from   6   to   108   months   with   a   mean   of   67.6   months.

Results: The overall survival rate at the last follow up was 81.25% (13 patients), three patients (18.75%) died at 6, 10, 16 months postoperative from distant metastasis. Fourteen of the 16 gastrocnemius muscle flaps survived without complications. In 2 patients, infection developed three weeks after surgery. In one patient the infection subsided after multiple measures, while in the second, amputation was performed to save patient’s life. The mean Musculoskeletal Tumor Society Score at follow-up was 81.2% (range, 74-90%) and the mean range of motion was satisfactory with only extension lag 5-15 degrees in the ten patients with prosthetic replacement.

Conclusion: The use of the medial head gastrocnemius muscle flap after wide excision and skeletal reconstruction of aggressive proximal tibia tumors provides successful soft tissue coverage and durable reconstruction of the extensor mechanism with satisfactory functional outcome. It is technically easy, safe and reliable, with a high survival rate and with minimal donor site morbidity if any. The well-vascularized muscle flap can combat wound infection and minimize wound dehiscence.

Introduction:

Limb salvage surgery has become an alternative procedure to amputation surgery in approximately 85-90% of malignant bone

tumors. Nowadays, it is the standard modality for treatment of malignant bone tumors around the knee in many centers. It was generally accepted that limb sparing surgery leads to an

increased risk of local recurrence, but there is no convincing evidence that it leads to decreased survival. A high rate of local recurrence suggests either inadequate margin of resection or inadequate adjuvant therapy.1-3

The goals of limb salvage surgery are complete eradication of the tumor with minimal complications, while maintaining acceptable functional, durability and cosmetic appearance of the limb.3 The procedure consists of three surgical phases: complete tumor resection strictly following the principles of oncologic surgery to avoid local recurrence, bone defect reconstruction, and finally, adequate soft tissue coverage is mandatory to decrease morbidity.4,5

Resection of extremity large bony sarcoma results in significant loss of muscles, large bone defects and sometimes, loss of the entire joint. The options available for reconstruction of bone defects after resection of a bone tumor around the knee include the use of a custom total knee prosthesis, an osteoarticular allograft or an allograft- joint replacement composite, an arthrodesis with intercalary bone-grafting, or conversion to rotationplasty.6 After resection of proximal tibia tumors, no deep fascia remains anteriorly which leaves the metal endoprothesis inadequately covered by fat and skin alone.7

Thus, the most serious problem encountered is the lack of enough soft tissue coverage, which is the direct cause of delayed wound healing, exposure of prosthesis and infection. Another difficult aspect is the need for reconstruction of the extirpated extensor mechanism.8

The gastrocnemius muscle is frequently employed as a local muscle flap for coverage of soft tissue defects in the upper third of the leg and lower third of the thigh,9-11 because of its reliability, easiness of design, size of muscle bellies, and minimal disabilities caused by its use.12 The medial gastrocnemius transposition flap has been reported to be used in limb salvage surgery around the knee to provide enough soft tissue coverage and recently to reconstruct the extensor mechanism.13-14

In the current study we present our 9 years experience of performing limb-salvage surgery

for management of malignant bone tumors of the proximal tibia. The reconstructed bone defects were covered with the pedicled medial head gastrocnemius muscle flap which was used also to reconstruct the severed extensor mechanism to allow a biological repair. The clinical and functional results will be presented.

Patients and methods:

Sixteen patients with aggressive benign and primary malignant bone tumors at the proximal tibia underwent limb-salvage surgery and were followed up in the period between October

2000  and  October  2009,  at  Ain  Shams

University Hospitals. They were 8 males and

8 females, with a mean age of 24.4 years at time of surgery [range 13-58 years]. The right lower limb was affected in 10 patients (62.5%) and the left side in 6 patients (37.5%). Pain and swelling were common presenting symptoms in all the cases. Five patients presented with pathological fracture (two with giant cell tumor and three with osteosarcoma). Another two patients with giant cell tumors, were treated previously by curettage and filling the cavity with cancellous and/or bone cement, presented by aggressive local recurrence Table(1).

Preoperative workup:

All the lesions were staged by standard plain radiographs of the lesion site and lung, computed tomography and /or magnetic resonance imaging and isotope bone scan. The diagnosis was confirmed histologically by an open or CT scan guided biopsy. According to the staging system of Enneking et al,15-19 the lesions were 4 aggressive benign lesions (25%) and 12 primary malignant bony lesions (75%), one of the malignant lesions was grade IB while the other 11 were grade IIB, Table(1). The tumor types were osteosarcoma (nine patients), malignant fibrous histiocytoma (one patient), chondrosarcoma (two patients), and giant cell tumor (four patients). All the patients with osteosarcoma and malignant fibrous histiocytoma received chemotherapy in the form of three courses preoperatively and five postoperatively.

Table (1): Details of the study group.

Surgical technique:

The limb-salvage surgery included, en bloc tumor resection, skeletal reconstruction, and soft tissue reconstruction.

Step 1 (Tumor en bloc excision):

An intra-articular wide resection of the proximal tibia was performed in all the cases as there was no evidence of tumor within the joint Figures(2C,3C&E). The biopsy tract is excised with a width of 2.5 cm with the biopsy scar in the middle down to the lesion. Thick fasciocutaneous flaps are elevated anteriorly and posteriorly to avoid skin necrosis. Then, we start dissection from normal healthy tissue, and if the muscles were infiltrated, a 5 cm safety margin from the soft tissues was considered.

The major neurovascular bundles were dissected free and retracted away from the dissection lines. The patella tendon was transected 1-2cm proximal to its insertion on the tibial tubercle. Once the proximal tibia has been exposed distally to a tumor free margin, an osteotomy is performed 3-5 cm from the edge of the lesion to achieve wide surgical margins depending on whether the tumor is of a low grade or a high grade malignancy, and the tumor is then removed en-bloc Figures(1C,D,2C,3C).

Step 2 (Skeletal reconstruction):

The skeletal defect was reconstructed by a modular prosthesis replacement system for proximal tibia in 10 cases (62.5%) Figures(1F,2D,E). Knee joint fusion with reconstruction of the defect by pedicled fibular transfer in 3 cases (18.75%) Figure(4), and non-vascularized fibular grafting in 3 cases (18.75%) with internal fixation Figures(3D,G).

Step 3 (Soft tissue reconstruction):

The technique for coverage of the proximal tibia prosthesis / fibular graft and reconstruction of the patellar mechanism is based on the anterior transfer of the medial gastrocnemius muscle. The muscle flap is not developed until the prosthesis has been cemented into position or the fibular graft has been transferred and stabilized. The medial gastrocnemius muscle flap was then dissected by identifying and dividing along the median raphe to separate the medial belly of the muscle from the lateral, and then distally along its musculotendinous junction, including part of its distal attachment to the Achilles tendon. The medial head of the gastrocnemius muscle is transposed anteriorly to cover the body of the prosthesis/fibular graft as well as the knee joint, while preserving its blood supply. The medial sural artery must be protected during the popliteal exploration and ligation of the geniculate vessels Figures(1C,D). The muscle flap can be rotated both transversely and proximally to cover large defects in either direction, where it is sutured to the remaining muscles and joint capsules. Appropriate reconstruction of the extensor mechanism was considered in the ten patients in whom no joint fusion was performed. At first, the patellar tendon is sutured to the loops or the holes on the tibial prosthesis with non- absorbable sutures. Then, it is sutured directly to the distal tendinous segment of the muscle and /or to the proximal edge of the transposed muscle flap (medial border of the gastrocnemius muscle with intact fascia as a functional unit) to restore the continuity of the extensor mechanism Figures(1E,2F,3F,4E).

Figure (1): Case (15) Giant cell tumor at the proximal tibia in 26 years old male, (A) X-rays demonstrating the aggressiveness of the lesion, (B) MRI showing extent of the lesion with complete destruction of the proximal tibia, (C) Dissection and preservation of the sural vessels, (D) Complete retraction of the posterior tibial vessels with intact sural branches, (E) Medial head gastrocnemius muscle flap covering the prosthesis, sutured to the remaining muscles and to the patellar tendon to reconstruct the extensor mechanism  and (F) Post- operative x-rays showing the prosthesis with good alignment.

Figure (2): Case (1) Osteosarcoma at the proximal tibia in 17 years old male, (A) A-P& lat x-rays showing the good response to the adjuvant chemotherapy, (B)MRI showing extent of the lesion with destruction of the proximal tibia with soft tissue extension, (C) Wide intra-articular resected proximal tibia with the included biopsy scar , (D) ) Modular endoprosthesis tibial replacement system bridging the defect, (E) x-rays showing the prosthesis with good alignment and stability 3 years postoperatively, (F) ) Medial head gastrocnemius muscle rotational flap covering the entire prosthesis and sutured to the extensor patella tendon and (G) One year postoperative,   showing   good  soft  tissue  healing  and  coverage  of  the  prosthesis.

Figure (3): Case (8) Osteosarcoma at the proximal tibia in 17 years old female, (A) A-P& lat x-rays showing the good response to 3 cycles preoperative chemotherapy, (B)MRI showing extend of the lesion with destruction of the proximal tibial metaphysis and epiphyseal infiltration with soft tissue invasion , (C) wide intra-articular resected proximal tibia with the included biopsy scar with the empty tumor bed , (D) ) Non - vascularized fibular graft augmented with bone paste bridging the defect, (E)Resected specimen with normal soft tissue cuff all around with intact articular surface, (F) ) Medial head gastrocnemius muscle rotational flap covering the graft  and (G)  Two years follow up x-rays showing knee fusion with bridging bone.

Figure (4): Case (6) Osteosarcoma at the proximal tibia in 13 years old female, (A) A-P& lat x-ray showing the good response to neo-adjuvant chemotherapy with healing of the pathological fracture, (B)MRI showing extend of the lesion with destruction of the proximal tibia with intramedullary extend, (C) Wide intra-articular resected proximal tibia with long diaphyseal part , (D) ) Pedicled fibular transfer with knee joint fusion with plate fixation (E) Medial head gastrocnemius muscle rotational flap covering the transferred fibula, sutured to the remaining muscles  (F) Post operative x-ray showing the transferred fibula in place and (G) 18 months post operative x-ray showing marked fibular graft   hypertrophy with good healing.

Post operative management:

Antibiotics were given intravenously for 3-

5 days, and continued orally for another one week to prevent infection. The operated leg is elevated and low molecular weight heparin (Enoxaparin 40 i.u) once daily as a prophylaxis of DVT, till the patient is fully ambulant. Adequate analgesia and /or sedation was given in the first few days postoperatively. Suction drainage was continued for several days to avoid the formation of hematoma or seroma in the operation site. A long posterior slab was applied for 4-6 weeks to protect the repaired extensor mechanism in cases with endoprosthetic replacement. A protection brace was applied  in cases with fibular graft and joint fusion till graft incorporation and good healing (average 4-6 months).

All the patients with osteosarcoma and malignant fibrous histiosarcoma received postoperative  five  courses  of  adjuvant chemotherapy   after   stitches   removal.

Postoperative follow up:

Plain X-ray films, antero-posterior and lateral views, were taken in the first 24 hours. Thereafter, the patients were followed in the out-patients clinic at regular intervals, every

2 months for the first year and then every 6 months. Clinical and radiological evaluation to assess joint stability, implant status and bone graft healing, and early detection of local recurrence or pulmonary metastasis were performed at each visit.

The functional evaluation was performed using the modified system of the Musculoskeletal Tumor Society,20 which is based on six parameters including: pain, functional activities, emotional acceptance, use of external support, walking ability and gait.

Results:

In 14 of the 16 patients, the gastrocnemius muscle flaps (87.50%) survived completely without complications. In two patients (12.5%) infection developed around the prosthesis, in spite that the muscle flaps were viable, which was managed with antibiotics according to culture and sensitivity, repeated debridement, irrigation and drainage for several months.

One of the two patients was controlled and become clean with some degree of affection of the functional score. The second patient did not respond to the conservative measures and necessitated an above knee amputation to control  the  infection  after  26  months.

At the last follow-up 12 patients (75%) were alive and free from any signs of local recurrence or systemic metastasis, and are rated as good to excellent. One patient is still alive and disease free after amputation for severe uncontrolled local infection at the surgical site. Three patients (18.75%) died from distant lung metastasis at

6, 10, and 16 months respectively, and these patients were excluded from the mean functional score for the study group. The mean disease free survival was calculated as 67.6 months (ranging from 30 to 108 months).

The functional follow up evaluation revealed that the mean postoperative score for the group studied (13 patients) was 81.2% (range from

74-90%). The mean range of motion was satisfactory with only extension lag 5-15 degrees in the ten cases with prosthetic replacement.

Discussion:

The proximal tibia is the second most common site for bony sarcomas. Surgical options for treatment of lesions in this area are grouped into two different alternatives, limb ablative, and limb sparing surgeries. Until the mid-1980s, almost all high-grade sarcomas of the proximal tibia were treated by mid-thigh amputation. This was because of the absence of adequate soft tissue coverage of the prosthesis or an allograft and difficulties in reconstructing the extensor mechanism.14-21

The outlook was poor and still, many patients died from distant metastasis. However, over the past two decades there have been significant advances in surgical techniques and adjuvant therapy that allowed for limb-salvage along with appropriately wide resection of primary bone sarcomas that do not alter the five year survival rates.14,21,22 Moreover, limb- sparing surgeries have been shown to have a trend for increasing 5 year survival and decreasing recurrence rates, provided it is preceded by accurate diagnosis, patient selection, and treatment planning.23,24 This is confirmed by

the high survival rate in many reports,24-28 and that achieved in the present study, which amounts to more than 80% patients’ survival after 9 years follow up with limb salvage.

Although the concepts associated with proximal tibia resection are relatively uniform among surgeons, reconstruction of the proximal tibia and knee joint and extensor mechanism reconstruction with soft tissue coverage vary from surgeon to surgeon.22 Reconstruction of the bone and joint defect is usually done with endoprostheses or allografts.7,22,29 The endoprosthesis are readily available and can allow immediate weight-bearing. Most of our patients (10 patients) were managed with total knee endoprosthetic replacement.

The principal technical difficulties with prosthesis in the proximal tibia region include, inadequate soft tissue coverage given the subcutaneous nature of the proximal tibia, and restoration of the extensor mechanism of the knee. Historically, these problems have led to salvaged limbs with poor functional outcomes and subsequent revision amputations.22 Now, it is generally accepted that, attention to soft tissue reconstruction is the key to a successful prosthetic or allograft reconstruction of the proximal tibia and knee region. This study describes the use of the medial head gastrocnemius muscle as a local flap for coverage of prosthetic material, extensor tendon repair for stability of the knee joint, and to bring a well vascularized tissue to avoid the complications of skin necrosis, wound dehiscence, and infection following limb- salvage  surgery  in  the  proximal  tibia.

The medial head of the gastrocnemius muscle has large size, so coverage of an extensive defect can be achieved which makes it an ideal flap for tumor surgery in the proximal tibia. It is easily accessible from the same operative field. Its dissection is easy and safe because it is vascularized by a dominant proximal vascular pedicle, the medial sural artery, which also makes it easy to evaluate its postoperative viability within a couple of days.24 As it provides a sizable, well vascularized tissue to the tumor resection site, so it can perform satisfactory soft tissue coverage, combat wound infection, support vascularity of the overlying skin flaps and prevent wound dehiscence. In the current study

the survival rate of the flap was 100% which could be compared favorably to other reports.8,10,14, 24 The flap maintained its viability even in the two cases complicated by wound infection, where in one of them the infection subsided and the other needed amputation to save patient’s life. So the infection rate in our series is 6.25% which is consistent with other reports7,21,30, and is attributable mainly to the muscle transposition flap.

Successful direct reattachment of the patellar tendon to the prosthesis is difficult because bone does not grow dependently into porous- coated surfaces as the interfaces are subjected to strong tension,31 entailing the risk of detachment of the patella tendon from the prosthesis.8 Recently, the medial gastrocnemius muscle flap has been used to reconstruct the extensor mechanism which is another challenge in limb-salvage surgery of the proximal tibia. This technique was first reported by Malawer.25

Augmented reattachment of the patellar tendon with Dacron tape or Dacron tube in combination with medial gastrocnemius transfer was further reported by Bickels21 and Buchner24 but the functional outcome of these reports were not very satisfactory. In Bickels’ study, only 78% of patients achieved a full extension to extension lag of 20 degrees. Nineteen percent of patients had an extension lag of 20-30 degrees, and an extension lag of

40 degrees was found in 1 patient (3%). Buchner reported that the mean MSTS was

75.1 % but the mean range of motion was only

60 degrees with 6 degrees of mean extension lag. In our study the mean MSTS score was

81.2 % (range 74-90%) and the mean range of motion was satisfactory with only extension lag 5-15 degrees in the ten cases with prosthetic replacement, in addition, no detachment of patellar tendon occurred in our group which proves the effectiveness of this technique of extensor tendon repair.

In conclusion, the use of the medial head gastrocnemius muscle flap provides satisfactory soft tissue coverage and durable reconstruction of the extensor mechanism with satisfactory functional outcome in limb-salvage surgery of aggressive bone tumors of the proximal tibia. It represents a practical, easy, and successful reconstructive option, with minimal donor site morbidity.

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