360 ABSTRACTS

knots in the simple suture configuration likely contrib- uted to its superior strength characteristics compared to the mattress suture configuration.

Tension Mismatch in Rotator Cuff Repairs: A Cause of "Controlled Failure" of Repair in Cyclic Loading. Stephen S. Burkhart, Todd C. Johnson, Michael A. Wirth, Kari Athanasiou, George Constan- tinides, and Gabriele Niederaur. San Antonio, Texas, U.S.A.

Crescent-shaped rotator cuff defects were created in 16 cadaver specimens by excising, in each specimen, a 1 x 2 cm crescent of tendon that comprised the supraspinatus insertion and a portion of the infraspi- natus insertion onto the greater tuberosity of the hu- merus. This effectively shortened the muscle-tendon unit acting at the center of the defect, in comparison with the muscle-tendon units at the periphery of the defect. The defect was repaired by transosseous simple sutures (#2 cottony Dacron in 8 specimens, and #2 Ethibond in 8 specimens) placed in a precisely stan- dardized manner. Each repair was then cyclically loaded by a servohydraulic materials test system acti- vator at a rate of 33 mm/sec to a load of 180 N, which is roughly equal to 50% of a maximal contraction of the involved muscles in an average human adult. A progressive gap in the repair was noted in each speci- men. A 5-mm gap developed at an average of 24.94 cycles (33.00 cycles for Dacron and 16.88 for Ethi- bond). A 10-mm gap developed in all specimens at an average of 182.75 cycles (195.88 for Dacron and 169.63 for Ethibond).

In three intact controls without defects in the rotator cuff, no gaps developed in any of the three specimens, each of which was cycled greater than 3,500 times to 180 N. This study suggests that rotator cuff tears that are repaired with a "tension mismatch" will undergo gradual failure with physiological cyclic loading until the normal resting length of the muscle-tendon unit is restored. This "controlled failure" may explain resid- ual defects that have been demonstrated by ultrasonog- raphy and by arthrography in patients with "success- ful" rotator cuff repairs.

Outpatient Anterior Cruciate Ligament Recon- struction. Erin A. Felger and John C. Pritchard. Chi- cago, Illinois, and Fort Wayne, Indiana, U.S.A.

We designed a prospective study at an outpatient surgery center to determine the effectiveness of arthroscopically assisted anterior cruciate ligament re- construction (ACL) using middle third patellar tendon

autograft. The outcome of the surgery and the cost effectiveness of the procedure were evaluated.

Forty-eight of 57 patients who underwent this sur- gery performed by a single surgeon returned for a com- plete follow-up at a minimum of 6 months (mean 14 months). Postoperative follow-up included the KT- 1000 arthrometric evaluation, the International Knee Documentation Committee Form (IKDC), and the Lys- holm Knee Scoring Scale. Results for the KT-1000 were excellent with a mean maximum difference of 2.0 mm. Seventy-five percent of patients had <3 mm maximum difference. Eight trace Lachmans and one positive pivot shift were noted. No one had any sig- nificant loss of extension compared with the contralat- eral side, and only 3 patients had some degree of loss of flexion on the affected side. Patients completed a subjective evaluation of their experience with the sur- gery and with the outpatient surgery center. Their re- sponses ranged from excellent to poor with 94% of patients being pleased with their outcome. Two com- plications were noted, a patellar fracture and a superfi- cial portal infection, both of which responded to appro- priate treatment. In our community, cost savings were substantial and statistically significant (P < .01) at more than $3,000 per patient when compared with the cost of surgery with overnight stay at an inpatient insti- tution. Overall, our complication rate and results were comparable to values in similar studies; by doing out- patient surgery, the expected outcome was not jeopar- dized. The data supported a positive outcome of surgi- cal success, knee function, and cost for this procedure being performed in the outpatient surgery center.

Is An ACL Reconstruction Outcome Age Depen- dent? F. Alan Barber, David A. McGuire, Burton F. Elrod, and Lonnie E. Paulos. Plano, Texas, Anchorage, Alaska, Nashville, Tennessee, and Salt Lake City, Utah, U.S.A.

Introduction: The selection of the treatment for a torn anterior cruciate ligament must consider many factors including the patient's activity level, instability, and functional impairment. Previous concerns about the advisability of an ACL reconstruction in older pa- tients include healing delays, rehabilitation difficulties, stiffness, arthritis, and the actual athletic demands. Concerns about graft site morbidity have lead some to use allografts in older patients. The purpose of this study was to evaluate the outcome of ACL reconstruc- tions in patients 40 years old and older compared to those 39 years old or less done during the same time period.

Arthroscopy, Vol 12, No 3, 1996