Introduction: The anterior cruciate ligament (ACL) can be anatomically divided into two bundles: the anteromedial (AM) and the posterolateral (PL). These two bundles have unique contributions to load transfer across the knee joint.

Material and Methods: We retrospectively reviewed the clinical results of a consecutive series of 25 patients who underwent partial ACL reconstruction. In 22 cases AM bundle reconstruction was performed, and in 3 patients isolated PL bundle reconstruction was performed.

The 25 patients included 7 women and 18 men with an average age of 29.2 years at the time of surgery.

Preoperative evaluation was conducted using manual Lachman test, pivot-shift tests, KT-1000, magnetic resonance imaging and passive stress radiographs of both knees. In all cases preoperative clinical evaluation was graded C as per the IKDC scoring system. The preoperative side-to-side anterior laxity measured by means of the KT-1000 was 5.8 mm in case of AM bundle rupture and 4.3 mm in case of PL bundle rupture.

All the patients underwent single-bundle reconstruction of the ACL under arthroscopic assistance (one single incision technique).

In case of AM bundle repair, the type of graft used was all autologous and included bone-patellar tendon-bone in 14 cases, 4-strand hamstring tendons in 5 cases and 2-strand hamstring tendons in 3 cases.

In case of PL bundle repair, 2-strand hamstring tendons transplant was used in the 3 cases.

Results: In all cases, postoperative clinical evaluation was graded A as per the IKDC knee examination scoring system. No abnormal sagittal laxity was found with the Lachman manual test. Postoperative IKDC knee subjective evaluation score averaged 81.3 % [58–95] at an average of 9 months follow-up.

Postoperative side-to-side anterior laxity measured with KT-1000 averaged 0.46 mm in case of AM bundle rupture and 0.5 mm in case of PL bundle rupture.

Postoperatively, all the patients had full extension of the knee. The flexion was the same as contra lateral knee in 92 % of the cases. We had no postoperative complication.

Discussion: Diagnosis of partial ACL rupture is often difficult. If the AM bundle is torn, the Lachman manual test is soft and the pivot-shift test is more often equal or glide. If the Lachman manual test is intermediary between firm and soft and the pivot-shift test is clunk, PL rupture has probably occurred.

The size of the graft was smaller than in one bundle procedures and was matched with the size of the bundle reconstucted. Peroperative technical difficulties were to preserve the healthy bundle and to drill the femoral tunnel in case of posterolateral bundle reconstruction.

Conclusion: This study showed consistent postoperative results. If partial rupture of the ACL can be diagnosed, isolated AM or PL bundle reconstruction should be considered.