The fibula is a rare site of primary bone tumour; the most common location for both benign (58.3%) and malignant (71.4%) tumours is the proximal fibula (1). Approximately half of all tumours are malignant, with osteosarcoma, Ewing sarcoma and giant cell bone tumour being the most common, the incidence of osteosarcoma and giant cell tumour in the proximal fibula was 2.3 and 2.8-8% respectively (2). The incidences of osteosarcoma and giant cell tumour in the proximal fibula are 2.3 and 2.8-8%, respectively. The main clinical manifestations are pain, common peroneal nerve palsy and swelling (3,4). The proximal fibular cortex is thinner and has more muscles and ligaments attached; these anatomical features lead to a higher probability of proximal fibular malignancy invading the surrounding soft tissue and developing into an extraosseous compartment tumour (5).

The bone cortex at the proximal end of the fibula is relatively thin, and the tumour can easily break through the bone cortex and invade the muscle. Most patients have been found in Enneking stage IIB; therefore, when selecting limb salvage surgery, sufficient surgical boundaries should be identified to obtain good oncological results (4,6). There is no unified surgical plan for fibular proximal malignant tumours, and proximal fibula tumours are usually treated with limb salvage surgery for extensive or radical resection (2). However, the proximal fibula is adjacent to the common peroneal nerve, the anterior tibial artery and ligaments of the knee joint; therefore, complications such as knee instability, tumour recurrence, peroneal nerve paralysis and arterial dysfunction may occur after tumour resection (6).

The present study retrospectively analysed the data of patients with primary malignant and invasive tumours in the proximal fibula and discussed the postoperative oncological results, complications and postoperative functions of resection operation.

The basic information of the patients is listed in Table I; according to pathological classification, there were 10 osteosarcoma cases, 3 chondrosarcoma cases, 2 invasive giant cell osteosarcoma tumour cases, 1 epithelioid sarcoma case, 1 leiomyosarcoma case, 1 fibrosarcoma case and 1 lymphoma case. According to the Enneking classification, IB stage was found in 2 cases, IIA in 2 cases and IIB in 15 cases. The indicators of treatment modalities and prognostic follow-up are listed in Table II; a total of 3 patients underwent Malawer I resection, and 16 patients underwent Malawer II resection. The follow-up time was 11-174 months, with an average of 76.58 months. None of the patients had incision infection or skin necrosis; however, there were two patients with common peroneal nerve injury. Local recurrence occurred in three patients (two with osteosarcoma and one with leiomyosarcoma); all three patients underwent Malawer I resection. In addition, one patient underwent amputation, one patient underwent extensive resection and one patient underwent local radiotherapy. Seven patients developed pulmonary metastasis, of which four of these patients succumbed. After the resection of proximal fibula primary and invasive tumours, the biceps femoris tendon and lateral collateral ligament insertion point was reconstructed. After the reconstruction of the biceps femoris tendon and lateral collateral ligament, knee joint function was stable in all but one patient who reported self-perceived instability of the knee joint. The MSTS score at the last postoperative follow-up was 23-29 points, with an average of 27.26 points (90.87%; postoperative MSTS score divided by total MSTS score). The LKS was 65-84 points, with an average of 83 points. Most patients experienced pain relief and their daily life was not affected. Patients with permanent common peroneal nerve palsy needed to wear braces to walk after surgery. Two typical cases are presented in the figures, including an invasive giant cell tumour of the proximal right fibula treated with Malawer I resection (Fig. 1), and a chondrosarcoma of the proximal left fibula treated with Malawer Ⅱ resection (Fig. 2).

A rare primary malignant tumour of the proximal peroneal bone presents a challenge for orthopaedic surgeons owing to its proximity to the biceps femoris tendon, lateral collateral ligament, common peroneal nerve and anterior tibial artery (12,13). The classic surgical modalities for the treatment of proximal fibular tumours were first reported by Malawer in 1984(8). In the Malawer I resection for marginal excision, the common peroneal nerve is preserved, the tibial blood vessels are rarely ligated and cut off, and the superior tibiofibular joint is excised intragastrically (8). In the Malawer II method for extensive resection, the common peroneal nerve and the anterior tibial vessels are excised, and the tibiofibular joint is excised outside the joint (8). The avoidance of postoperative recurrence and metastasis are considered as the main reference indicators in limb salvage surgery; amputation should be performed in some cases, particularly in the following (14,15): i) A large range of malignant tumours that invade the tibia, ii) multiple invaded fascia compartments, especially the posterior deep compartment, and iii) previous biopsies and surgeries causing the contamination of multiple fascia compartments.

Results from the present study are consistent with those reported in the literature. For example, a previous study comprising 112 cases of proximal fibula malignant tumours, including 50 cases of amputation (45%), 29 cases of Malawer I resection (26%), and 24 cases of Malawer II resection (21%), reported that 56 (50%) patients had distant metastasis and 12 (11%) had local recurrence (3). In addition, local recurrence was found in six patients receiving Malawer I and in three patients with Malawer II resection. Takahashi et al (16) examined 13 cases of proximal fibular osteosarcoma; according to Enneking staging, there was 1 case of IA, 1 case of IIA and 11 cases of IIB. Limb salvage treatment was selected for all patients at the first operative treatment, seven cases were extensively resected, four cases were marginal resected, two cases were curettage, and six cases had local recurrence postoperatively. In the present study, 3 cases were treated with Malawer I resection and 16 cases with Malawer II resection. Postoperative local recurrence occurred in three patients, all of whom were treated with Malawer I, and pulmonary metastasis occurred in seven patients which treated with Malawer II.

During Malawer I and II resection, the lateral collateral ligament, the biceps femoris tendon and other structures that maintain the lateral stability of the knee must be removed to obtain a safe range of excision (17). For stability and good function of the knee joint postoperatively, the lateral stable structure of the knee joint should be reconstructed (18,19). Currently, the reconstruction of the biceps femoris tendon and the lateral collateral ligament after removing the proximal fibula tumour remains controversial. One study reported that the lateral collateral ligaments and free tendons should be fixed on the proximal tibia to restore knee stability (18). Malawer et al (8) and Faezypour et al (20) also been reported that the biceps femoris tendon and the lateral collateral ligament should be sutured to the surrounding tissues and the anterolateral joint capsule using non-absorbable suture, which is a simple reconstruction method. These studies found that none of the patients complained of instability of the knee joint, no arthrovarus was found on physical examination, and the medial stress test was negative (8,20). However, different opinions have been put forward in the relevant literature. In the study by Einoder et al (21), no reconstruction of the lateral stable structure of the knee was performed intraoperatively, and the average follow-up period was 33 months. Although there was clinical evidence of lateral knee instability in three patients, there was no dysfunction, and all six patients could return to their level of activity before disease diagnosis. It has also been suggested that even if the lateral collateral ligament and the tendon insertion of the biceps femoris are reconstructed during proximal peroneal excision and the knee is still unstable, the gait is not affected because once the ligament and tendon insertion are damaged, it is impossible to restore the original position (22). After reconstruction of the biceps femoris tendon and lateral collateral ligament in all patients in the present study, one patient reported self-perceived instability of the knee joint in, whereas knee joint function in all other patients was stable. Abdel et al (3) reviewed 112 cases of aggressive proximal fibular tumours and found no long-term knee instability in the 53 patients who underwent resection with lateral collateral ligament reconstruction at a mean follow-up period of 7.4 years, suggesting that ligament reconstruction is important for functional knee recovery following operation. Most of these previous studies have reinforced that, after the resection of proximal fibula primary and invasive tumours, the biceps femoris tendon and lateral collateral ligament insertion point was reconstructed. In our opinion, continuity of the biceps femoris tendon, lateral collateral ligament, lateral deep fascia and iliotibial band should be retained as much as possible, and the insertion of the biceps femoris and lateral collateral ligament should be reconstructed through the hole in the lateral cortex of the tibial condyle; these techniques can effectively reconstruct stability and restore knee function.

There are a number of complications after resecting proximal fibular tumours; in addition to common peroneal nerve injury or knee instability, complications may include synovial leakage, skin necrosis, wound infection and posterior tibial artery thrombosis (23). Of the 112 cases reported by Abdel et al (3), 14 (12.5%) had postoperative complications after resection of proximal fibula tumours; Malawer II resection was performed in these 14 patients, including 6 cases of wound infection, 2 cases of posterior tibial artery thrombosis and 2 cases of common peroneal nerve injury. There were two patients with common peroneal nerve injury, and none of the patients in the present study experienced complications, such as wound infection or arterial thrombosis, which may be related to the Malawer I resection used in most patients. Results from the present study are consistent with those of the literature.

There are some limitations to the present study. First, this was a retrospective study with a limited number of patients; therefore, studies with larger sample sizes are necessary. Second, this study lacked an appropriate control group; therefore, appropriate control groups are necessary. And last, the follow-up time was relatively short, and longer follow-up period are necessary.

In summary, for patients with aggressive tumours such as proximal fibular giant cell tumours or with osteosarcoma with good pre-operative chemotherapy efficacy, marginal resection can achieve safety and good postoperative function. For large tumours with high degree of malignancy and sensitivity to chemotherapy, extensive resection is necessary and feasible to reduce recurrence and metastasis. At the same time, reconstruction of the biceps femoris tendon and lateral collateral ligament after removing the proximal fibula tumour can achieve knee stability.