There is considerable controversy about whether cystic arthrosis is a primary or secondary phenomenon in the development of degenerative joint disease of the hip1,2,4,5,8,10,13,15,18. Proponents of the bone-contusion theory have suggested that a localized area of subchondral necrosis of bone resulting from repetitive microtrauma leads to cystic degeneration, leaving the articular cartilage intact1,2,4,8,13,18. Proponents of the synovial intrusion theory believe that traumatic defects in the articular cartilage allow intrusion of synovial fluid through subchondral microfractures, resulting in cystic degeneration5,10,15. Both groups of proponents agree that, in the later stages of degenerative osteoarthrosis of the hip, subchondral fractures, cystic collapse of the acetabulum, and diffuse degenerative changes predominate on both sides of the joint. Both groups also agree that it should be possible to slow the progression of the disease by timely and appropriate operative intervention.
Often, by the time patients who have pain in the hip secondary to degenerative joint disease are seen, there are characteristic roentgenographic changes, such as decreased joint space, increased subchondral sclerosis, subchondral cysts, and osteophytosis; thus, it is impossible to determine whether the cystic changes were the precursor of the late changes. This report illustrates the evolution of degenerative joint disease of the hip. The sequence of changes supports the theory that cystic arthrosis is a primary phenomenon that may precede and hasten the onset of osteoarthrosis in some patients.
*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.
†3855 Nobel Drive, Suite 2206, San Diego, California 92122.
‡Department of Radiology (C. S. R.) and Division of Orthopaedic Surgery (A. M. L.), University of Maryland, 22 South Greene Street, Baltimore, Maryland 21201.
Fig. 1 Anteroposterior roentgenogram of the hips, made in July 1988. The right hip appears normal, and there is a two-centimeter cyst in the left supra-acetabular region.
Fig. 2 Coronal T2-weighted magnetic resonance image, made in August 1991, revealing a very high signal intensity, which is characteristic of fluid within the cysts.
Fig. 3 Anteroposterior roentgenogram of the hips, made in January 1992, showing an increase in the size of the cyst on the left side as well as slight narrowing of the joint space and early marginal osteophytes.
Fig. 4 Anteroposterior roentgenogram of the pelvis and hips, made twenty-three months after the operation. There is evidence of some sclerosis and consolidation of the cysts.
A thirty-three-year-old man was involved in a motor-vehicle accident in July 1988; his automobile was struck from behind by a vehicle traveling at approximately sixty-four kilometers (forty miles) per hour. The patient had pain in the lumbosacral region and left hip, although there were no osseous injuries. Before the accident, he had had no symptoms related to the hip but he had a history of recurrent ganglia in the right wrist. The initial roentgenograms showed a two-centimeter supra-acetabular cyst on the left side. The right acetabulum appeared normal (Fig. 1).
Over the following three years, the pain in the left hip worsened with the activities of daily living. The patient also noted the insidious onset of pain in the right hip, although the pain in the back resolved fully. He continued to work as a carpenter but became increasingly uncomfortable when climbing a ladder or when working on an uneven surface (such as a roof). In August 1991, roentgenograms revealed slight enlargement of the left supra-acetabular cyst and numerous smaller cysts that had developed in the left and right supra-acetabular regions. There was no narrowing of the joint space and no alteration in the structure or density of either femoral head. Computerized tomography and magnetic resonance images showed no evidence of subchondral disruption, synovial hypertrophy, capsular thickening, or a soft-tissue mass. The magnetic resonance images confirmed the cystic nature of the acetabular radiolucent areas and revealed incomplete septation and fluid in the spaces (Fig. 2).
The patient had to stop working because of the constant pain and stiffness in the left hip. Roentgenograms showed progression of the cystic changes, and in November 1991 an open transiliac biopsy of the supra-acetabular region was done on the left side to rule out a neoplasm. The largest cyst was filled with serous fluid that was not viscous and with sparse tan hemorrhagic tissue. There was no evidence of a well defined cyst wall or communication with the joint space. Histopathological evaluation of the contents of the cyst revealed benign fibroproliferative tissue and chronic inflammatory cells. Bacterial and fungal cultures showed no growth. The patient was discharged to his home on the third postoperative day with instructions for partial weight-bearing on the left lower extremity for six weeks and a home program of physical therapy to maintain the range of motion of the hip and the strength of the abductor muscles.
Roentgenograms made in January 1992 showed further enlargement of the cysts in both hips (Fig. 3) and, for the first time, narrowing of the joint space and early marginal osteophytes were seen in the left hip. The patient continued to have severe pain in the left hip that prevented him from returning to work. Multiple trials of non-steroidal anti-inflammatory drugs had failed. He was offered the options of either an arthrodesis or a total arthroplasty of the hip and, after lengthy discussions of the changes in lifestyle as well as the advantages and disadvantages involved with each procedure, he chose the latter. He was fully aware of the restrictions after hip replacement, as well as the possibility of revision, but his primary goal was to return to full employment with less pain. He adamantly refused arthrodesis of the hip.
On January 23, 1992, a left total hip arthroplasty was done with the use of a porous-coated component and no cement. At the time of the operation, several one to two-millimeter defects were seen in the weight-bearing articular surface of the acetabulum. Each defect appeared to be filled with mucoid tissue. The defects were explored and each was found to communicate with a large loculated cystic cavity in the ilium. A small amount of mucoid tissue within the large cavity was easily evacuated. The findings on pathological evaluation of the contents were consistent with the previous results. The large cystic cavity was curetted through the smaller defects. The rest of the subchondral bone was left undisturbed, as was the surrounding cartilage. The acetabulum then was reamed, and there was no evidence of unroofing of the cysts; good bleeding bone was present. The cysts were packed with an autogenous graft from the femoral head and the cup was press-fit. Three screws were placed to secure the cup further. The rest of the procedure was that of a standard hip replacement.
Although there were few symptoms associated with the right hip, the cysts were increasing in size. The patient chose to have a concurrent transiliac ablation of the cysts with bone-grafting, with the hope of altering the course of what appeared to be a process similar to that in the left hip. The cysts contained a small amount of gelatinous straw-colored fluid with tan soft tissue that was centrally located within the cavity. No lining of the cyst wall was evident, and there was no obvious communication with the joint. Iodinated contrast material was injected into the cavity, and intraoperative roentgenograms showed no intra-articular communication. The cyst cavity was curetted and was filled with fresh-frozen irradiated cancellous allograft. Histopathological analysis revealed fibrocartilaginous and osseous tissue with foci of necrosis and mild chronic inflammation. There was no growth on bacterial and fungal cultures of material obtained at the time of the operation.
The postoperative course was uncomplicated, and the patient returned home on the ninth postoperative day. On the first postoperative day, he was allowed to sit in a chair and an exercise program was started to regain motion of the hip. He was instructed to use a four-point gait with crutches to limit weight-bearing bilaterally for six weeks. At twenty-three months, the patient had complete resolution of the preoperative pain in the left hip, a slight left abductor lurch, and mild incisional pain in the left hip. The right hip had been painless since the fifth week. Roentgenograms made at twenty-three months showed good placement of the components and partial consolidation and sclerosis of both supra-acetabular regions (Fig. 4). The patient returned to his former work as a carpenter and did not need analgesics.