Intra-articular ganglia arising from the posterior joint capsule of the knee.

Magnetic resonance imaging (MRI) is an effective method to evaluate cystic lesions of the knee. Intra-articular ganglia of the knee joint was considered to be rare before the advent of MRI. However, because an MRI is often used to diagnose knee pathology, the reported prevalence of intra-articular ganglia has increased. We describe two cases of an intra-articular ganglion arising from the posterior joint capsule. Both cysts appeared to be arising from the posterior cruciate ligament by both MRI as well as arthroscopy through a lateral infrapatellar portal. However, arthroscopy through a posteromedial portal revealed the cysts to originate from the posterior joint capsule. It suggests that some of the ganglion arising from the posterior cruciate ligament reported in the literature might actually be from the posterior joint capsule. To prevent recurrence of a ganglion cyst, when preoperative MRI shows the mass to be located posterior to the cruciate ligaments, we recommend that the relationship of the ganglion cyst to the posterior joint capsule be evaluated at arthroscopy through the posteromedial or posterolateral portal.

Measurement of carpal canal and median nerve pressure in patients with carpal tunnel syndrome.

Carpal tunnel syndrome is a compression neuropathy wherein the median nerve is compressed inside of the carpal canal. Its diagnosis is made clinically, electrophysiologically, and sometimes by carpal canal pressure measurement. The objective of surgical management of this condition is the decompression of the median nerve. We usually measure carpal canal pressure preoperatively and postoperatively using a continuous infusion technique for diagnoses as well as for postoperative evaluation of decompression following our Universal Subcutaneous Endoscope system procedure. To evaluate whether our procedure effectively decompressed the median nerve, we measured intraneural pressure preoperatively and postoperatively in the resting position, with active power grip, and in the Okutsu test position. Correlation between the carpal canal pressure and intraneural median nerve pressure was statistically analyzed using the Kendall rank correlation coefficient (n = 157 hands). A significant correlation was present preoperatively in resting position and postoperatively with active power grip and in the Okutsu test position. Because of this correlation, we conclude that our endoscopic operative procedure effectively decompresses the median nerve and that simple carpal canal pressure measurement is sufficient to confirm diagnoses and to evaluate the status of postoperative decompression.

Discoid medial meniscus.

A discoid medial meniscus is an extremely rare anomaly. We present 4 cases of symptomatic discoid medial meniscus. Furthermore, magnetic resonance imaging (MRI) of the unaffected knee was obtained in 3 cases, and 1 patient had bilateral discoid medial menisci as well as a unilateral discoid lateral meniscus proven by MRI. Another patient had bilateral discoid medial menisci. In one of the other 2 cases, an MRI of the unaffected knee was not obtained. However, in the involved knees of both cases, medial and lateral menisci were discoid. The incidence of bilateral discoid medial menisci is unknown. In the past, the diagnosis of a discoid meniscus was made with an arthrogram or at arthrotomy. Therefore, whether some of the unilateral cases reported in the literature might have been bilateral is unknown. The reported prevalence of bilateral discoid medial menisci will probably increase, because when a discoid medial meniscus is encountered currently, an MRI is used to find knee disorders, including in the contralateral knee. Axial multiplanar gradient-recalled-echo imaging could provide images of the discoid meniscus, depicted in its entirety in one section. This would make the recognition of a discoid meniscus simple.

Tissue response to porous hydroxyapatite ceramic in the human femoral head.

We describe pathohistological findings of the human femoral head after it was grafted with hydroxyapatite (HA) and allogenic bone. The femoral head was removed because of the recurrence of a giant cell tumor 15 months after the graft. Histological investigation revealed that the entire surface of the HA granules was completely surrounded by the bone in the periphery of the grafted area; in some areas granules were partly in contact with the existing bone, and the rest were surrounded by fibrous tissue. There was no intervening layer of fibrous tissue between the granule surface and the bone where they were in direct contact. Pores were completely filled with fibrous tissue, partially filled with bone in the periphery of the pores, or completely filled with bone. Undecalcified histology revealed the formation of osteoid and ossification at the site where fibrous tissue infiltrated the pores. These findings indicated continued ingrowth of new bone into the HA pores. Under a scanning electron microscope, the surfaces of the granules showed clear demarcation in vitro, but it became less smooth, indicating in vivo changes. Although no foreign body reaction to the HA was noted anywhere, the HA surface appeared to be subject to a biodegradation process.

Dexamethasone enhances osteoclast formation synergistically with transforming growth factor-beta by stimulating the priming of osteoclast progenitors for differentiation into osteoclasts.

Long-term administration of glucocorticoids (GCs) causes osteoporosis with a rapid and severe bone loss and with a slow and prolonged bone disruption. Although the involvement of GCs in osteoblastic proliferation and differentiation has been studied extensively, their direct action on osteoclasts is still controversial and not conclusive. In this study, we investigated the direct participation of GCs in osteoclastogenesis. Dexamethasone (Dex) at <10(-8) M stimulated, but at >10(-7) M depressed, receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast formation synergistically with transforming growth factor-beta. The stimulatory action of Dex was restricted to the early phase of osteoclast differentiation and enhanced the priming of osteoclast progenitors (bone marrow-derived monocytes/macrophages) toward differentiation into cells of the osteoclast lineage. The osteoclast differentiation depending on RANKL requires the activation of NF-kappaB and AP-1, and the DNA binding of these transcription factors to their respective consensus cis-elements was enhanced by Dex, consistent with the stimulation of osteoclastogenesis. However, Dex did not affect the RANKL-induced signaling pathways such as the activation of IkappaB kinase followed by NF-kappaB nuclear translocation or the activation of JNK. On the other hand, Dex significantly decreased the endogenous production of interferon-beta, and this cytokine depressed the RANKL-elicited DNA binding of NF-kappaB and AP-1, as well as osteoclast formation. Thus, the down-regulation of inhibitory cytokines such as interferon-beta by Dex may allow the osteoclast progenitors to be freed from the suppression of osteoclastogenesis, resulting in an increased number of osteoclasts, as is observed in the early phase of GC-induced osteoporosis.

Acetabular labrum entrapment following traumatic posterior dislocation of the hip.

In traumatic dislocation of the hip with or without a fracture of the acetabular rim, complete anatomical reduction might be prevented by a bone fragment or infrequently by a soft tissue block, such as a torn acetabular labrum, ruptured capsule, or round ligament. We report a rare case of a tear in the acetabular labrum that prevented complete reduction of the dislocated hip. A 26-year-old man suffered posterior dislocation of the right hip, which was reduced under general anesthesia. The postreduction radiograph showed that the reduction was not complete, and a thin bony fragment was observed in the joint space in the weight-bearing area. Open reduction was performed 11 days later. We found a free bone fragment in the joint space, which was removed. The postoperative radiograph still did not show complete reduction of the hip. A large defect in the contrast medium was shown in the widened joint space by arthrography, which revealed the existence of the soft tissue interposition. We then performed a second operation and learned that the acetabular labrum was widely detached from the anterior to the posterior acetabular rim and was lying deep within the acetabulum. This detached portion of the labrum was excised, and the hip was reduced. The radiograph obtained during surgery then showed complete, concentric reduction. We missed the diagnosis clinically and radiologically at the first operation, proving how important it is to obtain an accurate radiological diagnosis in the operating room.

Bipolar revision arthroplasty for failed threaded acetabular components: radiographic evaluation of cup migration.

We studied the radiographic results of bipolar revision hip arthroplasty in 25 patients (25 hips). These patients had suffered from osteoarthrosis of the hip due to acetabular dysplasia and had undergone total hip replacement using smooth threaded acetabular components. In the revision surgery, these components were replaced by bipolar cups; autografts were implanted in 23 patients and hydroxyapatite grains were added in 7. At the time of follow-up, the severity of migration was radiographically graded from I to IV: grade I, 5 mm or less; grade II, 6 to 10 mm; grade III, 11 to 15 mm; and grade IV, 16 mm or more. Five to 11 years (average, 7.0 years) after surgery, 9 patients were classified as grade I, 6 as grade II, 4 as grade III, and 6 as grade IV. Among the 6 individuals with grade IV migration, hydroxyapatite grains had been used in 5. There was a significant negative correlation between the distance of migration and the increase in size of the threaded acetabular components used in the primary total hip replacement and the bipolar cups in the revision surgery. Because of the tendency to migrate, we concluded that this procedure has a limited role in revision surgery.

Ten-year follow-up of a proximal circumferential porous-coated femoral prosthesis: radiographic evaluation and stability.

We studied the radiographic findings on 48 hips in 48 patients to determine the stability of a proximal circumferential porous-coated femoral prosthesis in cementless total hip replacement. The patients had coxarthrosis related to acetabular dysplasia. The follow-up interval in the study was 10 to 13 years. In 36 patients, migration of the femoral component was equal to or less than 2 mm. No patient showed progressive migration. Revision surgery was performed in 37 patients because of migration of the acetabular components. Intraoperatively, no femoral components demonstrated visible motion under stress of the implant-bone interface, and none had been revised. During the follow-up period, two patients had mild thigh pain. Two others sustained fracture of the femur 11 years after surgery due to a fall. Pedestal formation was observed in 39 patients and calcar rounding in 21. The mean diameter of the medullary cavity around the distal part of the prosthesis increased from 13.6 to 16.3 mm average. We conclude that the proximal circumferential porous-coated femoral prosthesis is stable for more than ten years after surgery. The risk of subsequent periprosthetic fractures in elderly patients, however, is a matter of concern.