Monday, April 12, 2010

Excision of Proximal Fibular Tumors: A Newly Described Posterior Surgical Approach

The incidence of primary bone tumors in the fibula is 2.5%.1 The most common tumors found in the proximal fibula are osteochondromas, giant cell tumors, osteosarcomas, and Ewing’s tumors.2
Osteochondromas tend to grow eccentrically rather than centrifugally. Large osteochondromas that continue to grow after skeletal maturity have also been described.3 Osteosarcomas and Ewing’s tumors tend to grow in a centrifugal expansionist fashion, increasing in volume. It is therefore important to note the eccentric location of osteochondromas and their exact relationship to important anatomic structures such as the posterior tibial vessels and nerve, peroneal nerve, anterior tibial vessels, and fibular vessels.
A proximal fibular osteochondroma may distort the normal anatomical course of nerves and vessels and may lead to vascular compression syndromes and a pseudoaneurysm or peroneal nerve paralysis.4 The entrapment of a vessel in the cauliflower-like convolutions of an osteochondroma is also a possibility. A bursa may form about these lesions. An aggressive excision of these proximal tumors may lead to destabilization of the proximal tibiofibular joint.5 Careful staging and planning of the surgical approach and procedure is therefore of the utmost importance in dealing with proximal fibular tumors.
This article describes a surgical approach to deal with posteromedial growth of an osteochondroma that not only allows access and visualization at the posteromedial extension, but also at the anterior extension of such a tumor. At the same time, this approach allows for direct visualization and dissection of the posterior tibial vessels and for an extensive neurolysis of the peroneal nerve.

Case Report

An 18-year-old woman presented with a slowly enlarging posterior left calf mass. She reported exercise- and activity-induced pain with tingling and numbness in the sole of her foot. She had no previous history of tumors, and no one in her family had had any osteochondromas.
Clinical examination revealed a left calf greater in diameter compared to the right calf. The mass was present directly posterior in the calf and was firm in consistency. Both the dorsalis pedis and tibialis posterior pulses were palpable at the ankle. Muscle strength in the posterior tibial and peroneal nerve divisions was normal. No numbness was present during examination.
Radiographs revealed a large mass protruding from the fibula mainly posterior to the tibia (Figure 1). A diagnosis of a large osteochondroma was made. Magnetic resonance imaging (MRI) showed the mass to be extruding from the posteromedial surface of the fibula and extending medially and posteriorly (Figure 2). As this lesion was symptomatic and large, surgical excision was recommended. It was emphasized that nerve and vessel damage were possible. The patient elected to undergo surgery.
Figure 1: Lateral radiograph of an osteochondroma Figure 2: Axial MRI through the proximal fibular tumor
Figure 1: Lateral radiograph of an osteochondroma originating from the posterior aspect of the fibula and extending centrally into the calf muscles. Figure 2: Axial MRI through the proximal fibular tumor, demonstrating the dilemma of using a lateral or medial classic approach to the tumor.
The patient’s recovery was uneventful, with full neurological function without temporary nerve palsy postoperatively.

Surgical Technique

The patient is positioned in the right lateral decubitis position after a spinal anesthetic combined with conscious sedation. A tourniquet is applied on the upper thigh and elevated to 250 mm Hg prior to the incision.
A posterior longitudinal midline incision is used, starting at the flexor crease of the popliteal fossa laterally and extending 14 cm down the calf. Care is taken to preserve both the small saphenous and sural cutaneous nerves. The lateral portion of the incision is developed in the form of a large skin flap deep to the fascia to access the posterior and lateral compartments of the lower leg (Figure 3).
Figure 3: Lateral radiograph of an osteochondroma
Figure 3: Axial transverse anatomical illustration through the proximal third of the tibia with the surgical excision illustrated by dotted lines.
The median raphe of the gastrocnemius muscle is identified and cleaved. The lateral head of the gastrocnemius is carefully dissected loose from the soleus and mobilized laterally. The soleus is detached laterally and retracted medially, hence preserving its innervation on the medial side. The posteromedial part of the tumor can now be dissected free. The fibular attachment of the tumor cannot be accessed from this approach without damaging the lateral gastrocnemius. Therefore, the lateral border of the lateral gastrocnemius is now detached from the posterolateral intermuscular septum, allowing the muscle to be freed and able to be retracted medially or laterally to visualize and access the entire osteochondroma without damage to the lateral gastrocnemius muscle. Care is taken to preserve the proximal vascular supply and innervation of the gastrocnemius. The posterior vessels and nerve are visualized deep to the anterior border of the tumor.
The peroneal nerve is approached with the intent of mobilizing the common peroneal nerve and opening and exposing the common peroneal and deep peroneal nerve branch throughout the fibromuscular tunnel as described by Ryan et al.5 This is necessary to retract the peroneal nerve safely to a more anterolateral position to explore the tumor attachment to the fibula fully. It is imperative to ensure complete mobilization and release of the narrow part of the peroneal nerve through the fibrous tunnel to prevent postoperative compression on the nerve due to reactive swelling.
The next step is to carefully perform a subperiosteal dissection of the anterior periosteum of the tumor’s attachment of the fibula (the tumor stalk).
A curved Homan retractor is placed from superior around the stalk anteriorly to protect the anterior vessels. The tumor stalk is now carefully sectioned with a small oscillating saw. The stalk is retracted posteriorly and its anterior border can now be freed safely by dissection under visualization and protection of the posterior tibial vessels and nerve. Care is taken to remove the entire cartilage cap with its overlying membrane to minimize the possibility of a local recurrence. Sharp spikes of bone protruding from the fibula are smoothed, and visual inspection of the tumor bed as well as of the tumor on the back table is performed. The posterior tibial vessels and the peroneal nerve are inspected to ensure their free passage in the lower leg.
The tourniquet is released and all bleeders secured. The lateral gastrocnemius is sutured back posteriorly to the medial gastrocnemius. A soft drain is placed and the wound closed. A 3-way splint is applied with the ankle plantigrade (neutral) to prevent early muscle contracture and to help with pain management.

Discussion

Malawer2 described 2 types of excisions for tumors of the proximal fibula. The type I excision is wide but more conservative, saving the peroneal nerve and reconstructing the fibular collateral ligament. The type II excision, although also wide, is more aggressive and includes the anterior and lateral compartments, anterior tibial artery, peroneal artery, and proximal tibiofibular joint (en bloc). Both of these excisions are performed through a single incision curvilinear from above the knee, carving anterior to the tibial crest, and ending distal over the peroneal compartment. The flap is based on the posterior (medial) aspect of the skin. This is an excellent approach for centrifugally enlarging aggressive tumors where access to all 3 leg compartments is mandatory. The disadvantage of this incision is the large extent of the dissection to access the posterior compartment and its far medial extension to the medial border of the tibia.
It is for these medially protruding tumors not involving the lateral aspect of the fibula that the described surgical approach was developed. Krieg et al3 reported a case of extensive growth of an osteochondroma in a skeletally mature patient. Axial sections of the MRI showed a posteromedial extension of the tumor up to the medial border of the tibia. It would be difficult to access the entire tumor (similar to our case) from a lateral fibular approach without creating a large skin flap. A posterior midline approach in such cases allows the 2 heads of the gastrocnemius to be retracted sideways, exposing the medial and fibular (lateral) aspect of the tumor safely. If deemed necessary to reach the anterior compartment, it may be accessed by curving the incision anteriorly both at its superior and inferior extents (the reverse of Malawer’s2 skin incision) with its base anterior and lateral.
The incidence of iatrogenic peroneal nerve palsy after removal of fibular tumors is high (4 of 9 cases in the series of Erler et al6 and 3 of 6 type I excision patients of Malawer2). This shows the vulnerability of the common peroneal nerve and its branches after proximal fibular excisions. Palsy may follow excessive retraction or handling of the nerve with metal instruments, incomplete release of the fibular tunnel, and reactive postoperative swelling.
Ryan et al5 performed detailed anatomical dissections of the common peroneal nerve and its branches in the lower leg. They observed the most common site for compression to be the musculoaponeurotic arch at the entrance to the fibular tunnel. In cases of postoperative peroneal palsy, the entrance to the fibular tunnel is typically the area where the nerve is compressed. The deep peroneal nerve may be injured by procedures involving the lateral and anterior aspects of the proximal 8 cm of the fibula. It is therefore imperative to perform a complete release through the fibrous fibular tunnel and to retract the nerve only with soft instruments, eg, a rubber band to prevent iatrogenic peroneal nerve palsy. This is followed by applying adequate soft tissue coverage of the wound and by securing a 30° flexed position of the leg postoperatively.
Popliteal artery entrapment syndrome due to a fibular osteochondroma was described by Guy et al.4 Our patient had similar exertional symptoms due to posterior tibial artery compression. This diagnosis may be easily overlooked, and the claudication symptoms may be ascribed to muscle irritation and other mechanical causes of pain. Careful attention should be paid to preoperative MRI to assess any narrowing or compression of a segment of the posterior tibial vessels.
Tumor volumes >250 mL were reported by Erler et al6 as an indication to sacrifice the deep peroneal nerve to obtain a safe surgical margin. This applies to tumors with a high recurrence rate. Osteochondromas, even >250 mL, may be excised with sparing of the deep peroneal nerve with the caveat that a proper peroneal nerve release is performed.

Conclusion

Excision of benign or malignant tumors of the fibula prove challenging due to the intricacies of the local anatomy with tricompartmental involvement and the proximity of important neuromuscular structures. Careful attention should be paid to the exact anatomical location of the tumor and its involvement of important neurovascular structures in selecting a surgical approach best suited to minimize complications.

References

  1. Unni K. Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases. Philadelphia, PA: Lippincot-Raven Publishers; 1996.
  2. Malawer MM. Surgical management of aggressive and malignant tumors of the proximal fibula. Clin Orthop Relat Res. 1984; 186:172-81.
  3. Krieg JC, Buckwalter JA, Peterson KK, el-Khoury GY, Robinson RA. Extensive growth of an osteochondroma in a skeletally mature patient. A case report. J Bone Joint Surg Am. 1995; 77(2):269-273.
  4. Guy NJ, Shetty AA, Gibb PA. Popliteal artery entrapment syndrome: an unusual presentation of a fibular osteochondroma. Knee. 2004; 11(6):497-499.
  5. Ryan W, Mahony N, Delaney M, O’Brien M, Murray P. Relationship of the common peroneal nerve and its branches to the head and neck of the fibula. Clin Anat. 2003; 16(6):501-505.
  6. Erler K, Demiralp B, Ozdemir T, Basbozkurt M. Treatment of proximal fibular tumors with en bloc resection. Knee. 2004; 11(6):489-496.

Authors

Drs Lindeque and Oren are from the Department of Orthopedics, University of Colorado Health Sciences Center, Denver, Colorado.
Drs Lindeque and Oren have no relevant financial relationships to disclose.
Correspondence should be addressed to: Bennie G. Lindeque, MD, PhD, Department of Orthopedics, University of Colorado Health Sciences Center, Mail Stop B202, 4200 E 9th Ave, Denver, CO 80262 (bennie.lindeque@ucdenver.edu).
doi: 10.3928/01477447-20100225-14

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