The graft may fail in different ways, eg the graft may stretch or the fixation devices may migrate.
In deciding whether or not revision surgery is necessary, one needs to take a number of factors into consideration -
Based on the findings of the Lachman, pivot-shift, and KT-2000 tests, the graft can be classified as -
- partially functional
We classify partially functional grafts as those with a KT-2000 reading of 3-5.5 mm, a Lachman test only slightly positive with a hard stop, and a negative pivot-shift.
We classify non-functional grafts as those with 6 mm or more of anterior tibial displacement with the KT 2000, a positive Lachman test with a soft end point, and a fully positive grade 2 or 3 pivot-shift test.
Confirmatory radiographic evaluation
X-rays assess both the placement of the femoral and tibial graft tunnels, and any narrowing of the patellofemoral and tibiofemoral joints (to look for signs of joint surface deterioration or arthritis). In knees with failed ACL grafts, it is also important to determine if the patient's legs are abnormally bowed outwards (varus) or inwards (valgus), as this problem can cause reconstructions to fail. The surgeon first assesses the overall lower limb alignment with the patient standing. If it appears abnormal, then special x-rays are taken of both legs that go from the hips to the ankles. Measurements are then made of the weight bearing line, or where the forces are absorbed in the knee joint. The patient may have to undergo an operation called an osteotomy to realign the lower leg if the forces are not going through the center of the knee. Without this procedure, any graft (ACL, PCL, posterolateral) reconstruction has a high risk of failure.
1 Barber-Westin SD, Noyes FR, McKloskey JW. Rigorous Statistical Reliability, Validity, and Responsiveness Testing of the Cincinnati Knee Rating System in 350 Subjects with Uninjured, Injured, or Anterior Cruciate Ligament-Reconstructed Knees. Am J Sports Med. 1999;27:402-416.
2 Wroble RR, Van Ginkel LA, Grood ES, Noyes FR, Shaffer BL. Repeatability of the KT-1000 arthrometer in a normal population. Am J Sports Med. 1990;18:396-9.
3 Daniel, D. M.; Malcolm, L. L.; Losse, G.; and et al.: Instrumented measurement of anterior laxity of the knee. Journal of Bone and Joint Surgery, 67A: 720-726, 1985.
4 Daniel, D. M.; Stone, M. L.; Sachs, R.; and Malcom, L.: Instrumented measurement of anterior knee laxity in patients with acute anterior cruciate ligament disruption. American Journal of Sports Medicine, 13(6): 401-407, 1985.