JBJS | Article

The Journal of Bone & Joint Surgery, Volume 82, Issue 10

Articles | October 01, 2000

Flexible Intramedullary Nailing for the Treatment of Unicameral Bone Cysts in Long Bones*

Andreas Roposch, M.D.†; VinAy Saraph, M.S., D.N.B.‡; Wolfgang E. Linhart, M.D.‡

Investigation performed at the Department of Pediatric Orthopaedic Surgery, Karl-Franzens-University of Graz, Graz, Austria
*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.
†Spittelauerlaende 9/21, 1090 Vienna, Austria. E-mail address for A. Roposch: andreas.roposch@univie.ac.at. Please address requests for reprints to A. Roposch.
‡Department of Pediatric Orthopaedic Surgery, Karl-Franzens-University of Graz, Auenbruggerplatz 34, 8036 Graz, Austria. E-mail address for W. E. Linhart: wolfgang.linhart@kfunigraz.ac.at.

The Journal of Bone & Joint Surgery. 2000; 82:1447-1447

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Abstract

Background: Unicameral bone cyst is characterized by its tenacity and risk of recurrence. Pathological fracture is common and is often the presenting symptom. The objective of the present study was to evaluate the results of flexible intramedullary nailing for the treatment of a unicameral bone cyst with or without a pathological fracture.

Methods: Flexible intramedullary nailing for the treatment of a unicameral bone cyst was performed in thirty-two patients. Thirty of these patients presented with a pathological fracture; twenty-four were managed immediately with intramedullary nailing, and the other six had been managed conservatively at other clinics before they were referred to our department. The remaining two cysts were detected incidentally. The cyst was located in the humerus in twenty-one patients, in the femur in nine, and in the radius in two. The mean age of the patients at the time of surgery was 9.8 years, and the mean duration of follow-up was 53.7 months. Radiographic evaluation was performed according to the criteria of Capanna et al., and the cyst was classified as completely healed, healed with residual radiolucency (osteolysis), recurred, or having no response.

Results: The healing period ranged from three to 105 months. Fourteen cysts healed completely, and sixteen healed with residual radiolucent areas visible on radiographs. There was recurrence of two cysts that had healed with residual radiolucency. All of the cysts in the present study responded to treatment. A change of nails was necessary in nine patients, as the nails had become too short after bone growth. No major complications were observed.

Conclusions: Flexible intramedullary nailing provides early stability, which allows early mobilization and thus obviates the need for a plaster cast and decreases the prevalence of the most common complication: a pathological fracture. This method of treatment also allows for an early return to normal activity.

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Introduction

Introduction | Materials and Methods | Results | Discussion | References

The objective of treatment of unicameral bone cysts in children is to prevent a pathological fracture and to elicit healing of the lesion. Since Virchow³⁹ first described this entity in the nineteenth century, numerous articles have presented results of management. Earlier treatment methods included crushing of the cyst walls and the use of onlay grafts², total resection (diaphysectomy) with bone-grafting^{10,17,27,28,38}, subtotal resection without bone-grafting²⁶, and subtotal resection with bone-grafting^1,16.

Because of a better understanding of the pathology of unicameral bone cysts, surgical intervention now focuses on removing only the pathological bone or on stimulating osteogenesis within the cyst. Currently performed surgical procedures include curettage combined with bone-grafting^29-31, allografting with freeze-dried crushed cortical bone³⁷, use of homologous spongiosa chips³, the application of high-porosity hydroxyapatite¹⁹, and cryosurgery³⁵. Decompression with multiple drill-holes^{11-13,15,21,23,36} and intralesional injections of either steroids^4,5,14,18,34 or bone marrow^25,40 have also been used to treat unicameral bone cysts, with variable success.

Flexible intramedullary nailing for the treatment of unicameral bone cysts has been previously reported²³. This method is rapidly gaining popularity for the treatment of cysts in long bones because it is simple, surgical intervention is minimal, the results are predictable, and early mobilization is possible without the need for a plaster cast^9,20,32,33. We have been performing this method of treatment at the Department of Pediatric Orthopaedic Surgery at Karl-Franzens-University of Graz for the last eleven years. In the present study, we describe the surgical technique and present the results of flexible intramedullary nailing in thirty-two children with a unicameral bone cyst.

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Fig. 1-A:: Figs. 1-A through 1-D: Radiographs of a thirteen-year-old girl with a pathological long spiral fracture in a unicameral bone cyst of the proximal aspect of the right humerus.
Fig. 1-A: Preoperative lateral and anteroposterior radiographs.

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Fig. 1-B: Lateral and anteroposterior radiographs made eight weeks after flexible intramedullary nailing. The fracture is stabilized, and the cyst is occupied by the nails. Note how far the nails can be directed into the metaphysis without causing damage to the growth plate.

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Fig. 1-C: Lateral and anteroposterior radiographs made seven months after the nailing. Both the fracture and the cyst have healed.

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Fig. 1-D: Lateral and anteroposterior radiographs made twelve months after the nailing. The nails have been removed, and the cyst has healed completely. Note the thickening of the cortical margins of the cyst wall.

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Fig. 2-A:: Figs. 2-A through 2-D: Radiographs of a thirteen-year-old boy with a comminuted pathological fracture of the proximal aspect of the right femur through a unicameral bone cyst.
Fig. 2-A: Preoperative anteroposterior radiograph.

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Fig. 2-B:: Lateral and anteroposterior radiographs made immediately after flexible intramedullary nailing. After a closed reduction, the nails were passed through the lesion to stabilize the fracture, with care taken to avoid encroachment of the nails onto the growth plate.

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Fig. 2-C:: Anteroposterior and lateral radiographs made eight weeks after the nailing, showing bridging callus and the healing fracture.

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Fig. 2-D:: Lateral and anteroposterior radiographs made thirteen months after the nailing. The unicameral bone cyst has healed completely, and the cortical margins have thickened. The neck-shaft angle is similar to that on the contralateral, uninvolved side.

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Thirty-two patients with a unicameral bone cyst were managed with flexible intramedullary nailing between 1989 and 1997. There were twenty-five male and seven female patients between two and 15.5 years old (mean, 9.8 years old) at the time of surgery. These patients were followed for a mean of 53.7 months (range, twenty-five to 105 months).

The cyst was located in the proximal third of the humerus in twenty-one patients, in the proximal third of the femur in nine, and in the distal third of the radius in two. Five of the humeral bone cysts were located immediately adjacent to the physis. However, the femoral bone cysts were located in the femoral neck and in the pertrochanteric and subtrochanteric regions. Of the thirty-two patients, thirty presented at our institution with a pathological fracture and twenty-four were managed immediately with intramedullary nail fixation. In the remaining six patients, the pathological fracture had been managed conservatively, with cast immobilization, at other clinics before they were referred to our department. The cyst, which was located in the proximal aspect of the humerus in five of these patients and in the distal aspect of the radius in one, did not heal, although the pathological fracture healed in every patient. The period between the occurrence of the pathological fracture and nail fixation in these six patients ranged from two to twelve months. In the remaining two patients in the series, the bone cyst was detected incidentally on radiographs made because of minor trauma.

Surgical Technique

Prior to insertion of the nails, a percutaneous biopsy was performed under image-intensifier control. A small incision was made, and the cortical bone was exposed by blunt dissection. The location of the hole punch in the lesion was rechecked with the image intensifier, and adequate tissue was obtained. Histological findings showed a unicameral bone cyst in all of the patients in the present study.

After the biopsy specimen was taken, retrograde nailing was performed. Displaced pathological fractures were first reduced. Children with a lesion in the upper extremity were placed supine on the operating table, and displaced fractures in these patients were reduced manually. Patients with a lesion in the proximal aspect of the femur were placed on the fracture table because of the ease of fracture reduction, the possibility of accurately localizing the cyst and its relation to the femoral physis, and the ability to position the nails optimally.

We used stainless-steel Pediatric Ender Nails (Herndlofer, Vienna, Austria)²⁴, which are flexible and are inserted retrograde. These nails are 2.0 to 3.5 millimeters in diameter and thirteen to thirty-five millimeters in length. The diameter and length of the nails were selected on the basis of measurements made with a tape on the preoperative anteroposterior radiograph, with the enlargement on radiographs taken into account. The chosen length of the nails was then rechecked with the image intensifier after placement of the nail on the anterior surface of the corresponding bone. The longest nails that did not encroach on the proximal growth plate were used. The diameter of the nails was selected such that two nails would occupy approximately two-thirds of the medullary canal.

Two straight incisions were made in the distal region of the involved part of the extremity, medially and laterally, approximately three centimeters proximal to the joint line. The cortical bone was exposed by blunt dissection; under image-intensifier control, medial and lateral holes were made with an awl proximal to the distal growth plate. Both nails were directed to pass through the bone cyst, one at a time. The proximal and distal physes were carefully avoided. The distal opening of the nail was left protruding from the bone (Fig. 1-A, Fig. 1-B, Fig. 1-C, and Fig. 1-D). The stability of the fixation was checked by rotating the limb and looking for any movement of the fragments under an image intensifier. The incision was closed in layers. Muscles and the subcutaneous tissue covered the prominent part of the nails.

Postoperative Rehabilitation

The postoperative mobilization depended on whether there was a pathological fracture as well as on the stability of the fixation. On the average, patients with a pathological fracture of the femur were allowed non-weight-bearing, crutch-assisted walking on the third postoperative day (range, first to seventh day). Progressive weight-bearing was allowed depending on the stability of the bone. When there was precarious stability of the bone due to extensive cortical thinning, non-weight-bearing, crutch-assisted walking was encouraged for two to three weeks. Weight-bearing was gradually allowed after some healing of the fracture had occurred. Children with stable fixation of the pathological fracture were allowed to bear weight sooner. For upper-extremity lesions, the postoperative treatment consisted of mobilization exercises. Immobilization in a plaster cast was not used for either upper or lower-extremity cysts. The patients stayed in the hospital for a mean of seven days (range, five to fourteen days) and then were allowed to attend school after discharge. Sports activities were permitted once the fracture had healed and the cyst showed some consolidation. There was no restriction of sports activities for the patients who did not have a fracture. Clinical and radiographic follow-up was carried out in the orthopaedic outpatient clinic. Radiographs were first made at six to eight weeks, three months, and then every six months after the nailing (Fig. 2-A, Fig. 2-B, Fig. 2-C, and Fig. 2-D). Healing was assessed on plain radiographs according to the criteria of Capanna et al.⁶, and the nails were removed once the cyst had healed.

Results

Introduction | Materials and Methods | Results | Discussion | References

Results were evaluated on plain radiographs according to the classification system of Capanna et al.⁶. The cyst was classified as healed when it was completely filled with bone and the cortical margins had thickened. It was classified as healed with residual radiolucency (osteolysis) when most of the cyst was filled with bone and had healed, it was well consolidated with bone, and the cortical margins had thickened but there were still small, residual areas of radiolucency. The cyst was classified as a recurrence when it had healed initially and had become filled with bone but large areas of radiolucency and cortical thinning subsequently developed. It was classified as having no response when there was no evidence of any effect of treatment. Both recurrence and no response represented a failure of treatment.

Of the thirty-two unicameral bone cysts, thirty (94 percent) healed within thirty-six months (range, three to 105 months). Fourteen lesions (44 percent) were classified as completely healed and sixteen (50 percent), as healed with residual radiolucency. The follow-up period for the patients with a completely healed lesion ranged from twenty-five to seventy-eight months, and that for the patients with a healed lesion with residual radiolucency ranged from twenty-five to 105 months. Each lesion responded to treatment after the nailing. The patients with healing but residual radiolucency were still being followed at the time of this writing. The nails were removed at a mean of forty months (range, thirty-nine to fifty months) postoperatively.

Two recurrences (6 percent) were observed after the nails were removed. The first was in an eleven-year-old girl with a lesion in the proximal aspect of the humerus. Fifteen months after nailing, the cyst healed with residual radiolucency. The nails were then extracted. At a follow-up evaluation fourteen months after removal of the nails, a recurrent lesion was seen distal to the growth plate. A new nailing was performed and, at the time of this writing, the nails were still in situ. The second recurrence was in a ten-year-old boy who had a cyst in the proximal aspect of the femur (without a pathological fracture) that was classified as healed with residual radiolucency thirty-two months after nailing. A new area of osteolysis appeared distal to the growth plate six months after removal of the nails. The boy was then lost to follow-up.

The twenty-four bone cysts associated with a pathological fracture that was treated with immediate nailing healed at a mean of 36.4 months (range, three to 105 months). In the six patients who had intramedullary nail fixation after the fracture had healed following conservative treatment, the cyst healed at twenty-four to thirty-eight months. In the two patients who presented without a pathological fracture, the cyst healed at twenty-one and fifty-seven months. Because of the small number of patients in our study, we could find no statistical relationship between the healing periods for the patients with a pathological fracture and those for the patients without a fracture.

A change of nails was required in nine patients (28 percent) because the nails had become too short for the growing bone. The cyst was located in the humerus in six of these patients and in the femur in the remaining three. The age of the patients at the time of the first nailing ranged from 4.8 to 12.8 years, and the healing period ranged from twenty-seven to 105 months.

Five of the patients had a varus deformity of the proximal aspect of the femur after consolidation of the cyst. The deformity was less than 5 degrees in all of the patients. The articular-trochanteric distance was not altered, and none of the children had a Trendelenburg gait. Other complications, such as physeal damage, growth arrest, infection, refracture, or problems related to the protruding nail ends at the insertion site, were not encountered. Extraction of the nails was uneventful in all of the patients.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Unicameral bone cyst is characterized by its tenacity, its prevalence of recurrence after treatment, and its association with pathological fracture. To some extent, this explains the diverse methods used to achieve consolidation.

Curettage and bone-grafting has been the traditional treatment for unicameral bone cysts. Oppenheim and Galleno³¹ noted a complication rate of 17 percent, which included infection, coxa vara, epiphyseal arrest, and shortening of the limb. They found that the procedure had a high morbidity rate and concluded that curettage and bone-grafting should not be considered the treatment of choice for unicameral bone cysts. Major drawbacks of other surgical techniques, such as total or subtotal resection or saucerization, are physeal damage, large amounts of intraoperative blood loss, intraoperative fracture, and a prolonged period of postoperative immobilization^1,16,26,38.

Treatment of unicameral bone cysts with intralesional steroid injections, introduced by Scaglietti et al.³⁴, is based on the postulate that the membranous wall of the cyst degenerates after the injection of corticosteroids, thus eliminating the production of fluid in the cyst and the onset of osteoblastic activity. In our review of the literature, we found rates of healing of 67 to 96 percent, a 13 percent rate of recurrence, and a 6 percent rate of no response to that treatment^4-7,14,18,34. In most of the studies, multiple injections were used to treat recurrent cysts and cysts showing no response. Capanna et al.^6,7 reported that, of their ninety patients, one had avascular necrosis of the proximal femoral epiphysis after four steroid injections, seven had a pathological fracture during the course of treatment, and sixteen had shortening of the limb. Hashemi-Nejad and Cole¹⁸ reported on thirty-two patients and found good results in all nineteen children with a humeral or fibular bone cyst but in only nine of thirteen patients with a femoral or tibial lesion. They concluded that the healing response to intralesional steroids is unpredictable and that this treatment is usually ineffective even after multiple injections.

Bone marrow from the iliac crest has been injected percutaneously into the cyst cavity with the aim of stimulating bone formation in the cyst with the osteogenic elements in the autogenous bone marrow. Lokiec et al.²⁵ found consolidation of the cyst in all ten patients managed with this method. Yandow et al.⁴⁰ reported on twelve patients managed with this technique. Six of the cysts healed completely after one injection of bone marrow, and another two showed healing with residual radiolucency after three injections. Pathological fracture occurred in four of the patients during treatment, and two of the patients did not respond to treatment initially but were eventually successfully managed with curettage and bone-grafting.

Treatment with multiple drill-holes in unicameral bone cysts is based on the concept that the lesions are caused by the interstitial fluid that is unable to escape from the bone because of venous obstruction and blockage^11,12. Drilling of the cyst with Kirschner wires^11-13,37 or cannulated screws¹⁵ leads to a continuous decompression of the cyst because of drainage of fluid through the cyst wall. The decreasing internal pressure in the cyst is believed to be the essential feature of this method¹². Shinozaki et al.³⁶ reported on twenty-three unicameral cysts treated with drilling of multiple holes with Kirschner wires. Twelve patients in their study underwent a second surgery for the treatment of a recurrence. A third operation was necessary for three patients because of unsatisfactory consolidation of the cyst and the risk of a pathological fracture. The overall results of their study showed no recurrences, healing with residual radiolucency in eight patients, and complete healing in fifteen patients.

In 1981, Catier et al.⁹ reported successful results of flexible intramedullary nailing for the treatment of a unicameral bone cyst in the proximal aspect of the femur in two patients. Knorr et al.²⁰ and Santori et al.^32,33 reported complete healing in all of their patients. We suggest that the essential feature of this method is the same as that described in earlier series - namely, the continuous decompression of the lesion and the subsequent decrease in the intralesional pressure^11-13,21,36. However, we did not perform measurements of the intralesional pressure, and our assumption is based on the conclusions drawn by Chigira et al.¹¹.

The results of the present study show that flexible intramedullary nailing is an effective treatment for unicameral bone cysts. Thirty (94 percent) of the thirty-two lesions healed, and all of the lesions responded to treatment. In two patients (6 percent), the cyst recurred after initially healing. On the basis of a retrospective analysis of the radiographs of these two patients, we believe that the recurrent cysts grew outward from an area not covered by the nails. We did not observe any major complications in our study.

A review of the literature showed that approximately 50 percent of patients with a bone cyst have a complete pathological fracture and another 25 percent have infraction of a thinned cortex at the time of presentation⁸. Although local methods such as steroid injections, bone-marrow injections, and decompression produce consolidation in most patients, they offer no immediate mechanical stability to the weakened bone. Nailing has the benefits of decompression and providing early stability to the bone, which permits early mobilization, thus obviating the need for a plaster cast and decreasing the prevalence of the most common complication: a pathological fracture. In addition, this method of treatment allows for an early return to normal activity. Oppenheim and Galleno³¹ stated that the ideal treatment for unicameral bone cysts "should employ a low-morbidity procedure that has a low recurrence rate, prevents fracture, and allows a prompt return to normal life activity." On the basis of the results of our series, we believe that flexible intramedullary nailing is an effective treatment option for unicameral bone cysts in long bones. It is less invasive, prevents the occurrence of fractures, stabilizes pathological fractures, and allows a prompt return to normal activity.

References

Introduction | Materials and Methods | Results | Discussion | References

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