RECONSTRUCTION OF OLD ANTERIOR CRUCIATE LIGAMENT TEARS WITH A DACRON PROSTHESIS - A PROSPECTIVE-STUDY

Seventy patients with chronic anterior instability underwent anterior cruciate ligament reconstruction with a Dacron prosthesis pretensioned to 60 N. Of these patients, 49% (34) had combined medial instability, 32% (22) had failed previous anterior cruciate ligament surgery, and 37% (26) had previous meniscectomy. At reconstruction, 12 patients had their medial instability treated; 22 did not. Follow-up intervals wer e 3, 6, and 12 months and then each year to 5 years. The 5-year follow up included 69 patients; the other 1 had the ligament removed because of a synovial fistula at 8 months. Results were 23% prosthesis rupture s, 3% poor, 17% fair, 16% good, and 39% excellent. The 2-year results showed the same distribution, but a lower rupture rate, which was affe cted by placement of the tibial tunnel within the anterior one-third o f the tibia (9 times increase) and coexisting nonrepaired medial insta bility (5 times increase). Those patients with perfect placement of th e ligament who also had good medial stability and no previous ligament surgery had no rupture at 5 years. The stability that was gained at s urgery was gradually lost (-11.2% per year). At 5 years, the uninjured knee also had lost 41% of the preoperative stability; the mean laxity difference was within +/-2 mm. The mean improvement in subjective kne e function (Lysholm score 74.5 to 91.9) was maintained during the foll owup. The mean preoperative activity level improved significantly, but did not reach the preinjury level. These results show that the Dacron prosthesis will not give acceptable results in salvage cases where ot her instabilities are left untreated.