Comparison of polylactide screw and expansion bolt in bioabsorbable fixation with patellar tendon bone graft for anterior cruciate ligament rupture of the knee - A preliminary study

In a preliminary study, 24 patients with rupture of the anterior cruciate l igament (ACL) were operated an using implants made of self-reinforced poly- L-lactide (SR-PLLA). The operation method was outside-in bone-tendon-bone r econstruction. In 10 patients the fixation was made with an SR-PLLA screw w ith a diameter of 6.3 mm,in 12 with an SR-PLLA expansion plug with a diamet er of 6.0 mm, and in two cases both implants were used, but these cases wer e excluded from comparison. The purpose of the study was to evaluate and co mpare the use and fixation results of these two implants. The follow-up tim e averaged 3.2 years. Twenty patients attended follow-up. On subjective eva luations, seven of the eight patients following SR-PLLA screw fixation and six of the ten after expansion plug fixation regarded their knee as normal or nearly normal. Arthrometric testing showed the side-to-side difference t o average 2.9 mm following SR-PLLA screw fixation and 2.6 mm after expansio n plug fixation (NS). Six of the patients had giving-way symptoms (two afte r screw fixation and four after plug fixation). The pivot shift test was sl ightly positive in two patients and positive in one patient after SR-PLLA s crew fixation, and in three knees slightly positive and in another three kn ees positive following expansion plug fixation. Radiography showed variatio n in the location and orientation of the bone channels. Magnetic resonance imaging was performed in seven cases, and in two cases an edema was found i n the tendon of the anterior cruciate ligament graft and in six cases the i mplants were visible. No statistical difference in results between the SR-P LLA screw and SR-PLLA expansion bolt was noted. Fixation with expansion plu g seems technically more challenging, with a tendency to inferior results c ompared to screw fixation. In the absorbable fixation of a bone-tendon-bone graft there are no metallic artifacts on magnetic resonance imaging and no need to remove the fixation material regarding the revision surgery.