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OBJECTIVE: After surgical resection or repair of a torn meniscus, the healed area may have areas of abnormal signal intensity on MR images. Consequently, routine MR imaging is not reliable for detecting recurrent meniscal tears. As a result, we studied the efficacy of MR imaging with intraarticular contrast material (MR arthrography) for detecting recurrent tears of the meniscus. SUBJECTS AND METHODS: Thirty-seven patients who previously had a meniscal tear treated by either meniscal resection or repair had conventional MR imaging and MR arthrography with 40-50 ml of a 1:100 solution of gadopentetate dimeglumine in saline. All patients had arthroscopy shortly after the MR studies. Follow-up arthroscopic surgery was performed within an average of 6.6 weeks after the MR arthrograms. The routine MR images and MR arthrograms were reviewed separately and randomly, and these results were compared with the arthroscopic findings. Meniscal morphology, signal intensity, and the presence of joint fluid tracking into recurrent tears were evaluated. RESULTS: The overall accuracy in diagnosing recurrent meniscal tears in the post-operative meniscus was 66% when conventional MR imaging was used and 88% when MR arthrography was used. In patients who had only minimal meniscal resection, both methods had an accuracy of 89%. In patients who had more extensive meniscal resection, accuracy was 65% with conventional MR imaging and 87% with MR arthrography. In four patients who had only a small meniscal remnant, the accuracy was 50% with routine MR imaging and 100% with MR arthrography. On conventional MR images, the presence of an effusion tracking into a meniscal tear had a sensitivity and positive predictive value of 90% for detection of recurrent meniscal tears; however, the sensitivity was only 41%. CONCLUSION: Our results show that the sensitivity of MR imaging in detecting meniscal tears after surgery varies with the extent of the resection. Sensitivity was considerably improved when intraarticular contrast material was used. MR arthrography should be considered as an alternative to arthroscopy in patients who have had resection or repair of the meniscus.

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This article describes a new technique and instrumentation for performing arthroscopic distal clavicle resection safely and accurately using the three standard portals for shoulder arthroscopy. A simple six-step surgical technique is reviewed. Clinical results of patients who have undergone an arthroscopic Mumford procedure using this technique are presented also.

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The posteromedial compartment, particularly the posterior horn of the medial meniscus, has been shown by many investigators to be a common source of diagnostic errors in knee arthroscopy when access is limited to anterior portals. To better understand the anatomical basis of this apparent technical limitation, we quantified the visible versus the "blind" zones of the posteromedial meniscal periphery present when using the following arthroscopic approaches in six fresh knee specimens: (a) direct anteromedial frontal view with a 30 degrees arthroscope (AM-30 degrees); (b) anterolateral portal, 30 degrees arthroscope, transnotch view (AL-30 degrees); (c) anterolateral portal, 70 degrees arthroscope, transnotch view (AL-70 degrees); (d) central portal, 70 degrees arthroscope, transnotch view (C-70 degrees); and (e) posteromedial portal, 30 degrees arthroscope, direct rear view (PM-30 degrees). The AM-30 degrees approach visualized only the anterior 50% or less of the total superior meniscosynovial junction length, in all knees. The AL-30 degrees, C-70 degrees, AL-70 degrees, and PM-30 degrees portal approaches visualized the posteriormost 16.4%, 24.2%, 31.6%, and 54.9% of the upper meniscal rim, respectively. In conjunction with the AM-30 degrees visual field, the PM-30 degrees approach provided the most complete overall visualization of the superior meniscosynovial junction, leaving a mean blind zone of only 8.4% (12 mm) between the anterior and posterior visual fields. The AL-30 degrees, C-70 degrees, and AL-70 degrees approaches left significantly greater portions (means of 47%, 39.1%, and 31.7%, respectively) of the meniscal rim universalized.

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Growth plate chondrocytes isolated from the proliferative and hypertrophic zones of bovine costochondral junctions were grown in vitro in the presence of various oxygen tensions ranging from 3 to 60%. Using [35S] sulfate as an index of glycosaminoglycan synthesis, incorporation was found to be maximal at 21% O2. In contrast, proteoglycan aggregation under the same conditions was found to be maximal at 3% O2. There were no consistent differences in response between cells from the different morphologic zones even though they are exposed to different oxygen tensions in situ. These results show that proteoglycan synthesis and aggregation in growth plate chondrocytes in vitro are differentially affected by the ambient oxygen environment.

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In vitro monolayer cultures of growth plate chondrocytes isolated from newborn calf costochondral junctions were subjected to capacitively coupled electrical fields for 48 h. In part A, the electrical signal was a 60-kHz sine wave applied at different voltages so as to produce electrical fields at the pericellular level of 7, 20, 50, and 126 mV/cm. Incorporations of [3H]thymidine and [35S]sulfate were assayed to determine the effect of the above fields on cells proliferation and matrix synthesis, respectively. Proliferation was increased by 47% in the 20 mV/cm field whereas the same field decreased [35S]sulfate incorporation by 21%. These changes were significant at p less than 0.05 in both instances. In part B, the 20 mV/cm field was applied in a pulsed fashion to produce daily duty cycles of 100, 25, 2, and 0.25%. Incorporation of [3H]thymidine, [35S]sulfate, and [14C]proline per DNA were assayed. Results indicated that the 100, 25, and 0.25% percent duty cycles showed significantly (p less than 0.01-0.05) increased proliferation, whereas the 0.25% signal (5 ms on/495 ms off for 6 h/day) significantly decreased [14C]proline incorporation. We conclude that the biologic response of cells in vitro is signal specific, and that the total amount of electrical energy required to stimulate the growth plate chondrocyte to increased proliferation is very small since the total time the 0.25% duty cycle signal was only 3.6 min of a 24-h period.

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