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© 1996 The Journal of Bone and Joint Surgery, Inc. Tibial Stress Fracture after a Graft Has Been Obtained from the Fibula. A Report of Five Cases* , CLEVELAND , DECATUR, CLEVELAND, OHIO , DECATUR, GEORGIAInvestigation performed at the Departments of Orthopaedic Surgery, Case Western Reserve University, Cleveland, and Emory University School of Medicine, Decatur
Stress fractures of the lower extremity may result from overuse of normal bone or from normal loading of structurally deficient bone. Stress fractures of the pelvis have been reported as a complication after a bone graft has been obtained from the iliac crest4. Han et al. reviewed the cases of 160 patients who had had a vascularized bone transfer. Of the 132 patients who had had a fibular transfer, one had a tibial stress fracture but no follow-up information was provided. To our knowledge, no reports have addressed only fatigue failure of the tibia after the attainment of a graft from the fibula. We report the cases of five patients who had a tibial stress fracture after a graft had been obtained from the ipsilateral fibula for use in anterior reconstruction of the spine. Patients who have persistent or recurrent pain in the leg after a graft has been obtained from the fibula should be evaluated for a possible stress fracture of the tibia.
CASE 1. A sixty-eight-year-old woman who had spondylotic myelopathy had a three-level anterior cervical corpectomy with insertion of an autogenous fibular strut graft from the third to the seventh cervical vertebra. She had had an early natural menopause when she was approximately forty-one years old and had never received estrogen-replacement therapy. There was no history of smoking. A graft, six centimeters long, was obtained from the middle third of the left fibula with use of a power-driven microsagittal saw and periosteal elevators. Postoperatively, the patient was allowed to bear weight as tolerated and performed no specific exercises for the lower extremity. A cane was used for balance for approximately six weeks because of the severe myelopathy. The patient had an uneventful perioperative course and was seen at a routine follow-up examination six weeks postoperatively. She noted moderate pain in the left ankle and foot that was not worse with weight-bearing. No evidence of infection and only mild residual postoperative swelling were seen on clinical examination. The findings on plain radiographs of the leg and ankle were unremarkable, and ultrasound showed no deep-vein thrombosis. No specific treatment was recommended. The patient continued to bear weight as tolerated and no longer used the cane. The pain in the leg decreased, but it recurred in the middle region of the tibia and in the area of the ankle approximately four months postoperatively; it was worse with weight-bearing. Again, the findings on physical examination were unremarkable. The erythrocyte sedimentation rate was four millimeters per hour. Radiographic examination revealed focal periosteal new-bone formation along the lateral cortex of the tibial diaphysis and ill defined areas of linear sclerosis in the distal metaphysis (Fig. 1-A). A technetium-99m bone scan showed focal areas of increased radionuclide uptake in the mid-part of the diaphysis and in the distal metaphysis (Fig. 1-B). The diagnosis of a tibial stress fracture was made, and the patient was managed with a removable splint and with protected weight-bearing with use of a cane for three months. Repeat radiographs, made four months after the symptoms had recurred (eight months postoperatively), showed healing of the fracture. Radiographs made one year postoperatively demonstrated maturation of the periosteal new bone and resolution of the sclerotic changes in the tibial metaphysis (Fig. 1-C). The symptoms had improved substantially but had not completely resolved twenty-four months postoperatively.
CASE 2. A sixty-five-year-old woman with cervical kyphosis had anterior corpectomies with insertion of an autogenous fibular strut graft from the fourth to the seventh cervical vertebra followed by posterior stabilization and arthrodesis. A five-centimeter-long graft was obtained from the middle of the left fibula. She was a non-smoker, and the history included a hysterectomy and a unilateral oophorectomy when she was forty-two years old. She did not receive estrogen-replacement therapy until two years before the operation on the neck. The patient had an uneventful hospital stay. At the time of discharge, she used a walker for support but she could bear full weight on the limb. She used the walker for four weeks. At the six and twelve-week follow-up evaluations, she reported no pain in the lower limb. Approximately five months postoperatively, the patient noticed aching in the middle part of the left calf. She consulted her local physician, who reported that the findings on physical examination were not remarkable at that time. Approximately nine months postoperatively, the pain was more severe and radiographs of the lower extremity suggested periosteal new bone along the lateral cortex of the mid-part of the tibial shaft without evidence of a definite fracture. A technetium-99m bone scan showed increased activity in the middle of the left tibia that was consistent with a stress fracture and similar to the diaphyseal fracture in our first patient (Case 1) (Fig. 1-B). The patient was managed with a removable brace for three months and with protected weight-bearing with use of a walker for two weeks. The pain gradually decreased during the ensuing three months, and the left leg remained asymptomatic three years postoperatively. Because of the complete resolution of the pain, radiographs were not made at the follow-up examinations. CASE 3. A thirty-one-year-old woman had symptomatic iatrogenic lumbar kyphosis as a result of a remote posterior arthrodesis with Harrington instrumentation extending from the fourth thoracic to the fifth lumbar vertebral body, which had been performed because of scoliosis. She had a history of a chronic seizure disorder that was controlled with phenobarbital. The menstrual history was normal, and she did not smoke. The patient had a lumbar osteotomy with posterior instrumentation and arthrodesis as well as an anterior interbody arthrodesis at the disc space between the fifth lumbar and first sacral vertebrae with insertion of autogenous strut grafts from the iliac crest and the fibula. Six centimeters of the middle portion of the left fibular diaphysis was obtained. Postoperatively, the patient had a prolonged ileus, but the recovery was otherwise uneventful and she was encouraged to bear weight as tolerated. No walking aids were used. Approximately nine months after the operation, the patient noted pain at the fibular donor site. The pain increased with weight-bearing and was relieved with rest. The findings on plain radiographs were interpreted as normal, although in retrospect it was realized that slight periosteal new bone had been present. Two months later, radiographs clearly showed periosteal new bone along the lateral aspect of the tibial diaphysis. A bone scan confirmed the diagnosis of a tibial stress fracture at the level where the fibula had been resected distally. Weight-bearing was restricted for six weeks, which resulted in relief of the symptoms. By one year and three months postoperatively, the patient had little discomfort. Follow-up radiographs that were made eleven, fourteen, and twenty-one months postoperatively documented the progressive maturation of the periosteal new bone along the tibial diaphysis. CASE 4. A forty-one-year-old man who had symptomatic Paget disease of the third lumbar vertebra had a staged total spondylectomy after non-operative treatment had failed. Reconstruction included insertion of an autogenous fibular strut graft and anterior instrumentation. Approximately seventeen centimeters of the middle part of the fibular diaphysis was obtained at the operation. The patient had no history of smoking. Plain radiographs of the lower extremity had not been made preoperatively to rule out pagetic involvement of the fibula, but a preoperative total-body bone scan had demonstrated uptake in only the third lumbar vertebra. The patient had no perioperative complications and was able to walk with full weight-bearing and without aids on the third postoperative day. Sixteen months postoperatively, he noted pain in the distal part of the left leg, the area of the donor site. The findings on clinical examination were unremarkable except for local tenderness over the tibia. Plain radiographs demonstrated periosteal new-bone formation along the lateral aspect of the tibial diaphysis, and a technetium-99m bone scan was positive for a fracture. The patient was advised to restrict activity for six weeks, and within three months the symptoms had almost resolved. Because of the clinical improvement, follow-up radiographs were not made. CASE 5. A fifty-five-year-old woman had a three-level anterior corpectomy and insertion of an autogenous fibular strut graft for the treatment of cervical kyphosis and compression of the spinal cord. Six centimeters of the fibula was obtained from the mid-part of the left fibular shaft. She had smoked many years previously. She had had natural menopause and had been started on estrogen-replacement therapy two years before the operation. The patient was able to walk with use of a walker by the third postoperative day and could bear full weight on the limb. She used the walker for one week and then used a cane for four weeks. She had decreasing pain at the donor site during that time. At ten weeks postoperatively, however, she noted severe pain proximal to the ankle joint in the donor extremity. The pain was worse with weight-bearing and caused her to limp. On physical examination, she was found to have mild diffuse swelling and tenderness above the medial malleolus. There was no evidence of infection or of tenderness or swelling in the diaphyseal region. The findings on radiographs of the tibia and ankle were unremarkable. A technetium-99m bone scan showed increased activity in the distal metaphysis of the tibia that was consistent with a stress fracture. The patient was managed with a removable splint and use of a cane for six weeks. Radiographs made four months postoperatively showed mild sclerosis in the distal metaphysis of the tibia. At the most recent follow-up examination, six months postoperatively, radiographs showed that the sclerosis had resolved. The patient had no pain and no positive physical findings.
The frequency of stress fractures of the tibia after a graft has been obtained from the fibula is unknown. According to the hospital records at Case Western Reserve University and Emory University, approximately 350 fibular ostectomies had been performed for various reconstruction procedures since 1985. Whether this number represents a useful denominator is not clear. It is possible that tibial stress fractures occur with a greater regularity than has been recognized. As these fractures typically heal spontaneously, pain reported by patients most likely has been considered to be due to trauma to the soft tissue at the donor site. The load-bearing role of the fibula has been investigated under a variety of in vitro conditions7,9-13. Takebe et al. used uniaxial load-cells to measure the relative compressive forces across the sites of tibial and fibular osteotomies. They reported that the fibula transmitted only 6.4 per cent of the load with the ankle in a neutral position. In a study in which the proximal one-half of the fibula was resected and tibial strain gauges were used, Lambert concluded that the fibula was subjected to one-sixth of the weight-bearing forces. Whereas the compressive forces in the tibia were anterior and lateral before resection of the fibula, the distribution of the forces shifted toward the lateral aspect of the tibial diaphysis alone after resection. Lambert did not find that the interosseous membrane contributed substantially to strain resistance, but other authors10,12 found that division of the interosseous membrane reduced fibular strain by 30 to 50 per cent. Although the relative values differ, it seems clear from experimental data that the fibula plays a role in normal weight-bearing. Discontinuity of the fibula increases the loads on the tibia and alters the distribution of strain. This effect has been used clinically, alone and in conjunction with other methods of operative treatment, for non-union of the tibia2. We believe that the increased load on the tibia after a graft had been obtained from the fibula resulted in the tibial stress fractures in our five patients. None of our patients had an altered level of activity that might have been responsible for excessive loading. One patient (Case 1) was postmenopausal early in life, and another (Case 2) had had a unilateral oophorectomy; neither had a history of long-term estrogen-replacement therapy. They most likely had a relative degree of osteoporosis but were otherwise active individuals with limbs that were quite capable of normal load-bearing preoperatively. Another patient (Case 5) had a history of smoking, which is a known risk factor for osteoporosis1. The mechanism of this effect is believed to be increased hepatic metabolism of estradiol to less biologically active metabolites, which contributes to decreased bone mass8. One patient (Case 3) had been managed long-term with phenobarbital. This drug induces the hepatic microsomal P450 enzyme system in the liver and leads to accelerated hydroxylation of vitamin D to biologically inactive products3,5. This increased metabolism of vitamin D can lead to inadequate absorption of calcium, resulting in osteomalacia and decreased mechanical strength of the skeleton. Bone densitometry measurements were not performed on this patient to rule out osteomalacia, but there were no findings on plain radiographs of the spine or lower extremity to suggest decreased bone density. The onset of symptoms in our patients was not related to any known trauma. As is typical of fatigue fractures, the symptoms began insidiously from ten weeks to sixteen months postoperatively. The findings on clinical examination of each limb were unremarkable, with the exception of mild swelling in one patient (Case 5). The diagnosis was confirmed by radiographic and scintigraphic findings. The location of periosteal new-bone formation was lateral in all patients who had a diaphyseal fracture. This finding corresponds with the altered distribution of tibial compressive forces observed experimentally after fibulectomy7. We do not routinely apply a brace after a fibular ostectomy has been performed to obtain a graft, but we recommend use of a brace for patients who have osteoporosis or who expect to bear excessive loads. Although the prevalence of stress fracture of the tibia seems very low, we believe that an increased awareness of this potential complication will help in the recognition and treatment of tibial stress fracture in patients who have persistent or recurrent pain in the leg after a graft has been obtained from the fibula.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
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