Gene expression of collagen types IIA and IX correlates with ultrastructural events in early osteoarthrosis: new applications of the rabbit meniscectomy model.

OBJECTIVE: To examine the phenotypic expression and geographic distribution of collagens in early stages of osteoarthrosis and their relationship to ultrastructural events in cartilage. METHODS: In situ hybridization was used to localize articular expression of total type II (A+B) and type IX collagen at 2 and 4 weeks in the rabbit meniscectomy model of osteoarthrosis. The expression of the developmental marker collagen IIA was analyzed at the same time points. Articular cartilage structure was examined by scanning electron microscopy. RESULTS: Little difference was found in total type II or type IX collagen gene expression for operated versus control limbs at 2 weeks. Gene expression for collagen types IIA and IX was found to be site-specific by the 4 week period and was largely limited to the meniscectomy site. At 4 weeks, this activity was correlated with site-specific alterations in chondrocyte morphology, qualitative changes in the collagen matrix, and articular surface delamination on microscopy. CONCLUSION: Gene expression for collagen types IIA and IX is site-specific and correlates with ultrastructural changes in cartilage in this model of early osteoarthrosis. We present the first known report of the distribution of type IX collagen gene expression in any model of osteoarthrosis. These findings support the central importance of matrix interactions in osteoarthrosis and suggest that early phases of repair involve re-expression of a developmental sequence by chondrocytes.

Reflex sympathetic dystrophy of the lower extremity in tetraplegia: case report.

Reflex sympathetic dystrophy (RSD) of the upper extremities has been reported to occur following complete and incomplete injuries of the cervical cord. Such reports describe the value of the three-phase radionuclide bone scan (TPBS) in differentiating RSD from pain of other sources. To our knowledge, RSD of the lower extremities has not been reported in a patient with tetraplegia. We report a case of lower extremity RSD in a patient with complete traumatic injury of the cervical cord. The case illustrates the use of the TPBS to differentiate RSD from heterotopic ossification (HO) in the lower extremities. THe successful use of the alpha-adrenergic blocker, phenoxybenzamine, in the treatment of RSD is described. Follow-up to 30 months has shown no evidence of recurrence, and complete resolution of the scintigraphic findings.

Remodeling of articular step-offs. Is osteoarthrosis dependent on defect size?

One of the major unresolved questions in trauma repair concerns the degree of step-off that can be accepted in a joint surface. In answer to this question, a new rabbit model of femoral step-off was developed. Osteoarthrotic changes in cartilage and bone and the failure of repair responses were seen at 20 weeks in the presence of a 3-mm wide sagittal defect displaced 5 mm from the joint surface and spanning the anteroposterior extent of the medial femoral condyle. This study examined the effects of a similar defect, displaced 2 mm from the joint surface, to determine whether the development of osteoarthrosis is dependent on the size of the step-off. Defects were created in 18 New Zealand white rabbits. In a second group, the medial joint surface was osteotomized, but was not displaced. In contrast to th first study, cartilaginous and bony repair resulted in closure of the surgical defect and restoration of femoral congruity. Histologic and biochemical parameters did not differ significantly between groups. The results indicate that cartilage and bone possess the ability to remodel small articular step-offs and to restore joint congruity. Furthermore, the combined data suggest that the development of osteoarthrosis requires significant articular incongruity.

An experimental model of femoral condylar defect leading to osteoarthrosis.

The acute treatment of articular step-off injuries is based largely on reduction criteria, because the presence of residual incongruity has been correlated with the development of posttraumatic arthrosis (PTA). However, this association has not been demonstrated on a prospective basis. Using the rabbit femoral condyle, we developed a surgical model of articular condylar defect without sacrificing the axial alignment or inherent stability of the knee joint. Twenty weeks after the creation of 5-mm femoral condylar defects, progressive osteoarthritic changes were confirmed by radiographic, histological, and biochemical parameters. Osteophytes were observed on the medial aspect of operated knee joints in 67% of cases. Femoral and tibial articular cartilage at the site of the condylar defect exhibited fibrillation, hypocellularity, and severe loss of safranin-O staining. Focal areas of cartilage were denuded or replaced by pannus. In no case was femoral congruity restored by cartilage repair. Statistically significant decreases in proteoglycan content were demonstrated for cartilage sampled from the weight-bearing region of the condylar defect and from the tibial surface directly beneath it. These changes resemble those arising from previously reported models of osteoarthrosis. We present the model as a valid tool for the study of articular condylar defect and its role in the development of PTA.

Management of penetrating pneumatic nailgun injuries of the knee.

Of 36 patients who presented over a 3-year period with nailgun injuries, nine of these injuries were found to have penetrated into the knee joint. Six of these injuries were treated by operative nail removal, curettage of the nail tract, and examination of the joint. The remaining three patients had nail removal, followed by irrigation of the joint in the emergency room. All nine injuries had antibiotic prophylaxis before and after nail removal. In three of six patients treated by operative irrigation and debridement, a piece of clothing or nailgun resin was discovered in the nail tract or floating within the knee joint. None of the patients in the group treated by operative nail removal, joint visualization, irrigation, and nail tract curettage experienced any complications, whereas one patient treated nonoperatively developed a septic knee. Due to the unique nature of these nailgun puncture wounds, we strongly advocate operative nail removal, curettage of the nail tract, visualization of the joint, and use of prophylactic antibiotics in the treatment of nailgun arthrotomies.