Clinical comparison of freeze-dried and fresh frozen patellar tendon allografts for anterior cruciate ligament reconstruction of the knee

Abstract

The aim of this study was to evaluate the clinical outcome of freeze-dried compared to fresh frozen al lograft tissue used as a substitute for a ruptured ACL of the knee. In addition, the incidence of any graft rejection phenomena was recorded. Forty-one patients with ACL deficient knees underwent reconstructive sur gery using a patellar bone-tendon-bone allograft that had been freeze-dried (Group 1, N = 14) or fresh frozen (Group 2, N = 27). All patients underwent the same implant technique and rehabilitation program. Followup ranged from 24 to 36 months. The evaluation consisted of subjective, objective, and instrumented laxity testing (KT-1000, MEDmetric, San Diego, CA; and Genucom, FARO Medical Technologies, Inc., Montreal, Canada). There were 31 males and 10 females. Eleven (79%) patients in Group 1 thought their knee was "normal" or "improved," and 25 (93%) in Group 2 thought the same. In addition, 10 (71%) patients in Group 1 denied any "giving way," compared to 26 (96%) in Group 2. The mean Lysholm knee score in Group 1 was 86/100 (range, 22 to 100) compared to 92/100 (range, 59 to 100). Clinical examination included the Lachman test and tests for anterior drawer sign and pivot shift. Postop eratively, Group 1 patients had the following results: Lachman test—seven Grade 0, six Grade 1, one Grade 2; anterior drawer sign—eight Grade 0, five Grade 1, one Grade 2; and pivot shift—seven Grade 0, five "trace," and two "present." In Group 2, the results showed the following: Lachman test—17 Grade 0, 10 Grade 1; anterior drawer sign, 20 Grade 0, 7 Grade 1; and pivot shift—23 Grade 0, 4 "trace." The KT-1000 mean left-right difference in Group 1 was 1.2 mm (0.0 to 4.0 mm) compared to 0.9 mm (0.0 to 3.0 mm) for Group 2. The Genucom mean left-right difference in Group 1 was 1.30 mm (0.0 to 3.0 mm) compared to 1.5 mm (0.0 to 9.0 mm) for Group 2. Overall, there was a marked improvement in both groups relative to overall subjective and objective re sults, the fresh frozen recipients doing slightly better than those who received a freeze-dried allograft. Statis tical analysis revealed a significant difference in only 3 of the 21 parameters evaluated. There was no clinical evidence of rejection phenomena in either group.