OBJECTIVESTo measure the size and change of bone tunnel in arthroscopic assisted anterior cruciate ligament (ACL) reconstruction with hamstring tendon autograft by X-ray, and evaluate the incidence, extent, shape and reasons of the bone tunnel expansion and analyze the relationship between bone tunnel expansion and clinical results.

METHODSFifty-one cases of arthroscopic ACL reconstruction with hamstring tendon autograft were performed, and they were followed up at average of 16 months postoperatively. The diameter, shape, position and angle of femoral and tibial bone tunnel were measured using X-ray, and other clinical information had been collected including gender, age, method of tibial fixation, range of motion, KT 2000 and evaluation of muscle strength and so on. All data were entered into the computerized relational database to analyze and compare using the chi square test and correlation analysis.

RESULTSThe incidence of tunnel expansion after ACL reconstruction was 85%-94% in femoral tunnel and 65% in tibial tunnel. The extent of tunnel expansion was 51%-53% in femoral tunnel and 40%-44% in tibial tunnel. The most common shape of tibial tunnel was type O in the A-P X-ray view and type V in the lateral X-ray view. Femoral tunnels anterior to the expected ones were more likely to enlarge. Tibial tunnels anterior to the expected ones were easier to expand. An acute tibial or femoral tunnel angle could result in the femoral tunnel expansion.

CONCLUSIONSThe incidence and extent of bone tunnel expansion in arthroscopic ACL reconstruction with hamstring tendon autograft are more significant in femoral tunnel than in tibial tunnel. Bone tunnel expansion is correlated to patients' age, height, BMI and location of the tunnel. The main factors related to bone tunnel expansion are the location and angle of the tunnel.