CHAPTER 8 CHRONIC ANKLE JOINT PAIN: Subchondral Bone Cyst A Case History Stepben J. Miller, D.P.M. Chronic ankle joint pain can be a pafiicularly ...
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Miller, D.P.M.

Chronic ankle joint pain can be a pafiicularly challenging and sometimes perplexing problem, especially in patients who are avid athletes. Achieving solutions to such an enigma requires a thorough diagnostic work-up and a carefully designed treatment plan, often with a measure of creativity utilizing available technology. CASE HISTORY 45-year-old podiatrist presented with chronic, yet intermittent left ankle pain that he had been experiencing for the previous 10 years. He was


frustrated by its lack of response to treatment. In addition to training for and running in marathon races, he enjoyed a variety of other activities including rock climbing, bicycling, kayaking, and hiking. There was no known specific injury to the left ankle, but he did relate landing hard on his foot at times in the past when jumping down from ledge to ledge while rock climbing. The ankle pain, described as both a deep ache and at times as a sharp jolt from within the joint, had worsened over the past three years to the point where the doctor could no longer pursue weightbearing activities. Even standing in surgery was becoming intolerable, particularly when he would stand and rotate his torso with his foot remaining in a fked position. The podiatrist-patient had not noticed any joint swelling and could not tolerate ankle braces, compression ankle socks, or other supportive devices. The pain was relieved with rest and would extend on after pursuing weight bearing activities' Nonsteroidal anti-inflammatories provided mild relief, but were not pafticularly helpful. Intraarticular injections of steroids and local anesthetics provided immediate and almost total relief extending up to two weeks, followed by a return of pain. He had also tried three different types of orthotics because he was also plagued by a chronic cuboid syndrome. The orthotics did not help the ankle pain or the foot problem. Over the previous lwo years, lwo anterior approach afihroscopic ankle

surgeries had been performed: one by a local orthopedic surgeon, and a second procedure by an experienced podiatrist with the assistance of a Holmium-YAG Laser. The joint surfaces were reported as clear with only some mild fibrillar synovitis. Since the last surgery the patient also described pain in the anteromedial ankle gutter area, mostly anteromedially. This had also become worse over the past year. Physical examination revealed normal neufovascular status. There were tlvo small scars on the anterior side of the left ankle. The medial scar was tender with a palpable deep, tender, movable nodule at the joint line. Range of motion of the ankle was pain-free without any clicking or crepitance, but with some restricted dorsiflexion. Tenderness was noted upon deep palpation of the posterior lateral and posterior medial ankle joint at the confluence of the posterior ankle and subtalar joints. The subtalar joint had a pain-free range of motion and there was no tenderness noted in the sinus tarsi. At mid stance, there was a moderate amount of pronation which appearcd to be maximum for his range of motion. Unfofiunately, the graphite ofihotics being utilized failed to bring his feet to a neutral Position. The standard view radiographs showed no articular or peri-articular defects (Figs. 1A, 1B). Both the CT and MRI scans demonstrated a fluidfilled bone cyst 13 mm x 7 mm in diameter. The cyst was located in the subchondral tibial plafond, situated 1 cm from the posterior margin of the tibia and 2.5 cm from the external surface of the medial malleolus, and 1.5 cm from the lateral border of the lower tibia (Figs. 2-4). The CT scan showed the lesion more clearly, and indicated a possible posterior extension. A contrast medium CT scan was also performed. The contrast material did not seem to penetrate the ankle joint, ruling out articular communication and joint fluid pistoning (Figs. 5, 6). A diagnosis of subchondtal intra-osseous cyst was proposed as a source of this chronic ankle pain. Since conservative measures had been


Figure 1A. Lateral x-ray view of the ankle loint

Figure 18. Mortise x-ray r.iew of the ankle joint

Figure J. T2-weighted image of MRI scan, sagittal slice w.ith measuring markers,

Figure 2. T1-weighted image of the MRI scan. coronal


Figure 4 T2-u,eighted in'rage of the MRI scan showing cyst to be l1uid tilled.




CT arthrogram of the lefi ankle, AP view.

unsuccessful, a surgical plan was devised. Consultation was sought from two experienced ankle arthroscopists. It was determined that an arthroscopic approach to this lesion would be impossible without significant risk of damage to the joint and/or instrrmentation. Access via a medial malleolar osteotomy was declined due to the additional morbidity risk and the articular invasion necessary to access the cyst. The goal was to keep the catilaginous surface intact. Since the cyst was not visible on x-ray, fluoroscopy could not be used for direct visualizaiion of the cyst. Howeveq it was felt the location could be accurately determined using the measurements from the CT and MRI scans. Therefore, a plan was devised to angulate a guide pin and cannulate a drill bit across the tibia to access the cyst with Fluoroscan-guided assistance, then curette and pack the area with bone graft (Figs. 7-9).

Execution of the surgical procedure took place through a 3 cm longitudinal incision situated between 7 cm and 10 cm above the tip of the medial malleolus on the medial leg. Once the periosteum was reflected, a 0.045" K-wire was used to penetrate to the exact calculated position of the bone cyst using the Fluoroscan for guided assistance. Once this position was accurately reached, a 4.0 mm cannulated drill bit was placed over the pin and drilled down to the level of the cyst with care being taken not to enter the ankle joint. The length of the hole was a little more than 4 cm. A buck bone curette was then inserted and used to remove the cyst. The cyst fragments were sent for pathologic analysis which eventually confirmed that the specimen was "consistent with


Figure 6. CT arthrogram of the left ankle, lateral view. Notice the contrast does not enter the bone cvst.

osteochondral bone cyst."

At that point, liberal irrigation was used to flush out the drill hole which was then packed with autogenous bone graft pafiicles from the drilling. The length of the drill hole was then filled with a custom fashioned dowel allogenic bone graft from the Musculoskeletal Transplant Foundation (Edison, New Jersey). It was fashioned into a peg to fit snugly into the hole. The periosteum was sutured and the wound was closed in layers. A second surgical procedure involved excising the anteromedial ankle scar and entering the anteromedial ankle joint for an arthroplasty technique. The tissue was quite thick and scarified and the dissection carried down to the joint capsule which was then penetrated. Upon opening the joint capsule, there was a flap of scar tissue noticed to be irritating the shoulder of the talus. It was approximately .5 cm long and 1 cm wide. This flap was removed with sharp instrumentation, with care being taken not to damage the cartilaginous surface of the joint. The joint was further inspected and there was no synovitis noted and the cartilage was intact. After liberal irrigation, the ankle joint capsule was closed and the remaining tissues closed in layers. Early range of motion was started, as well as weight bearing after the first three postoperative days. Although the symptoms persisted for several months, at six months, the podiatristpatient was pain-free and was able to compete in a 150 mile bicycle race without discomfort. This case is a good example of utilizing technology in conjunction with a sound knowledge of anatomy to solve a challenging clinical problem to the benefit of the frustrated patient.




Figure 7. K-rvire guided u'ith Flr:oroscan assistance



Curette used to extract the cyst.

DISCUSSION Subchondral bone cysts fall within the classification of bone tumors and tumor-like lesions.' Often termed juxta-articular bone cysts, they are defined as "benign cystic and often multi-loculated lesions made up of fibrous tissue, with extensive mucoid changes located in the subchondral bone adjacent to

a joint. Radiographically, each appears as a welldefined osteolyic lesion with a surrounding arca of sclerosis. It has been described as a synovial cyst, but it lacks a synovial lining."'The cysts are usllally solitary, but may be multilocular, and commonly develop in the epiphyseal or metaphyseal areas of bone adfacent to joints. Generally, they have a whitish or bluish lining consisting of parallel bundles of collagen. The fibrocyes lying along the inner wall of the cavity sometimes form an incomplete lining of

Figure 8. Cannulated 4.0 mm drill bit.

flattened, synovial-like cells. These make for a smooth wal1 within which the cyst contains a thick gelatinous mucoid fluid.r 5 They are likely to communicate w-ith the joint through the articular surface in up to 40o/o of the cases, and therefore may be fil1ed with synovial fluid. Many theories have been proposed to describe the genesis of these 1esions.6 The early theories of "synovial fluid intrusion," either as a primary event from increased intra-articular pressure, or as a secondary event during the healing process when necrotic subchondral bone is removed, is more applicable to the subchondral bone cyst associated with arthritic disease or trallma. The role of trauma and compressive forces has been postulated, but the exact association remains unclear. In a recent suffey of intra-osseous ganglia (another name for subchondral bone cyst), out of 213 lesions, Murff and Ashry found the majority located in the distal tibia.'

Although cystic bone lesions may be asymptomatic, they commonly cause intermittent pain aggravated by increased activity. Joint movement by itself does not necessarily cause pain. The discomfort is thought to be caused by an increased intra-lesional pressure from the accumulation of fluid. However, on rare occasions, the pain may develop from fracture through the subchondral bone. These lesions tend to weaken the surrounding bone. If there is communication between the cyst and the joint, then the synovial fluid may move back-and-forth, pistoning between the two cavities. Occasionally, pain precedes the radiographic appearance of the lesion. More over, subchondral bone cysts have been reported to occur preceding


the subsequent diagnosis of inflammatory or degenerative arthritis. Such a cyst is often visualized on standard x-rays, well-defined in bone with a sclerotic rim around a radiolucency. However, it is better delineated using computed tomography (CT) which also helps determine if it communicates with the joint. To better determine the soft tissue components, as well as the nature of the fluid within the cyst, magnetic resonance imaging (MRI) is a more precise diagnostic tool. It is especially helpful in analyzing the contents of the cyst.8

The subchondral bone cyst should

be differentiated from aneurysmal bone cyst, giant cell tumoE chondromlxoid fibroma, cafiilage fumor,

unicameral bone cysts, Brodie's


REFERENCES Spjut HJ, Dofman HB, Fechner RE, Ackerman LV: Tumors of

3 4 5

Surgical treatment, once conservative measures have been exhausted, usually involves accessing the cyst and curetting it. Every attempt should be made to preserve the cartilaginous surface. However, if it is already destroyed then it behooves the surgeon to simply curette the cyst out and leave an open cavity within the joint which will fill in with fibrous tissue.e Another way to access the lesion is through the bone near the lesion. This allows use of a curette to extract the lesion and, if possible, pack it with bone graft. The success rate of curettage and packing is very high, with only a 7o/o tecLlffence rate reported. Since these lesions often occur in very odd locations, the surgeon must be both creative and resourceful. However, treatment is generally very rewarding with satisfactory results. The use of low radiation Fluoroscan imaging to accurately guide instrumentation to the site has been extremely beneficial.'o This is an example of applying current technology to a challenging surgical problem.

Bone and Cartilage. Atlas of Tumor Patbolog,t. 2nd Series, Fasc. 5. \Wasl'rington DC; Armed Forces Institute of Pathology; 1971. Schajowicz F, Ackerman LV, Sissons HA: Histologic typing of bone tumour. Intetnational Histological Classification of Tumors, Geneva: World Health Organization, 1.972. Schajowicz F, SlullitelJA: Juxta-articular bone cysts (Intra- osseous ganglia). J Bone Joint Surg, 6lB :107 -11.6, 1979. 'Woods CG: Subchondral bone cysts. Bone Joint Surg 438:7i8' J 765. t961. Bauer TW, Dorfman HD: Intra-osseous ganglion. A clinicalpathologic study of eleven cases. Am J Surg Patbol 6:207-273, 1982.

6. 7. 8.

osteomyelitis, and pigmented villonodular synovitis. It is not erosive; on rare occasions, the lesions of tuberculosis in bone may resemble the osteochon-

dral bone cyst.



F: Ganglia of bone: theories, manifestations, and presentations. Cit Reu Clin Radiol Nucl Med 4:303-332, 1973. Murff R, Ashry HR: Intra-osseolrs ganglia of the foot. J Foot Ankle Surg 33:396-401, 1994. Feldman

Kabbani 'WM, Mayer DP: Magnetic resonance imaging of osteochondral lesions of the talar dome. J Am Podiatr Med Assoc 84192-195, 1994 Guhl JF, Stone JW, Ferkel RD: Other osteochondral pathology fractures and fracture defects. In Guhl JF ed. Foot and Ankle Arthroscop!,2nd ed, Thorofar NJ; Slack; 7993: 135, 1,10-145. Siciliano CF, Lefkowitz H: Removal of an intra-osseous metallic foreign body in the calcaneus utilizing a fluoroscopically guided bone trephine. J Foot Ankle Surg33:83-86, 1994.