During the period of evaluation from December 1997 to April 1998, a total of 174 knees underwent ACL reconstruction using this technique. Complete two-year follow-up (mean 2.4 years) including IKDC forms and KT results are available for 49 patients. These data represent preliminary results on these patients for the BioScrew.

The average age of the patients in this study was 33.1 +/- 7.0 years (range 16 to 49). All patients had chronic ACL tears at the time of operation (more than three months after injury). Four patients had failed a previous ACL reconstruction, and two patients had undergone remote primary repair of their ACL. There were 37 males (76%) and 12 females (24%). Twenty-one right and twenty-eight left knees were affected. Associated surgical findings included chondromalacia, menis-cal tears, and loose bodies. A medial partial medial meniscectomy of less than one-third was performed in 21 cases (41%), a complete medial meniscectomy in 2 (4%), a partial lateral meniscectomy of less than one-third in 18 (36%), and a complete lateral meniscectomy in 1 (2%).

Follow-up KT tests showed an average laxity with a maximum manual force of 1.5mm ± 3.6mm at one year and 1.25mm ± 2.82mm at two years. Patients were further divided into categories of laxity with 33 (67%) patients having 0 mm to 2 mm of laxity; 13 patients (27%) having 3 mm to 5 mm of laxity, and 2 (4.1%) having greater than 5 mm of laxity. One patient in the greater than 5 mm laxity group and 3 patients in the 3 mm to 5 mm laxity group represented revision surgical procedures.

At final follow-up, one patient had a persistent effusion, one patient lacked 5° of extension, and four patients lacked 5° of flexion.

The Lachman test was normal in 32 patients, grade 1+ in 12 patients, and grade 3+ in two patients. One patient was felt to have mild PCL instability, and two patients had mild posterolateral instability on emergency room testing at 30°. At the final follow-up, four patients had a 1+ pivot glide, and one had a 3+ pivot shift. No instances of BioScrew breakage occurred.

Radiographs were taken of the knees at the two-year follow-up visit to complete the IKDC forms.

Tunnels were measured at their widest point, at the aperture, the midpoint, and 1 cm from the distal aspect of the tunnel. In 36 of the 49 cases (73%), the X-rays were available for secondary review of the tunnels. The morphology of the tunnel, the width of its widest point, the width of the aperture, and the cross-sectional area were measured and compared to mechanical outcome.

Significant tunnel expansion (Group C) was identified in 10 cases (28%). In these cases, the tibial tunnel was expanded in seven, and femoral tunnel expansion was identified in seven cases. In six cases, the expansion could be considered to be significant, with the widest point of both tunnels measuring 15 mm. Four of the ten cases in group C had between 3 mm and 5 mm of laxity at maximum manual force at the two-year follow-up mark. No significant correlations existed by comparison with the Spearman correlation coefficient between final IKDC score or KT-score or with the measurements of the tunnels at the aperture, midsection, widest point, or most distant part of the tunnel. In the five cases where both tunnels measured greater than 15 mm, on at least one radiograph, two cases were in the 3 mm to 5 mm group.

From the other perspective, 18 cases with available radiographs at two-years had less than 2 mm of laxity, seven had 3 mm to 5 mm of laxity, and one had greater than 5 mm of laxity on a maximum manual force KT examination. In four of the seven cases, the morphology of the tunnel could be classified as expansive as opposed to cylindrical and filling in with bone (57%). However in 6 of the 18 cases (33%) with less than 2 mm of laxity, similarly expansive tunnels were identified. The extent of aperture widening did not correlate with clinical laxity or IKDC score at two-year follow-up.

Multiple statistical comparisons were made to identify positive predictive factors, which resulted in an increased trend for a patient to fall into the 3 mm to 5 mm laxity group at two years. Specifically using post hoc ANOVA, ANCOVA comparisons, Spearman rank correlations, and unpaired two-tailed student t-tests, it was concluded that gender, patient age, the use of secondary tibial fixation, and the magnitude of preoperative instability and laxity could not be associated with an increased KT manual maximum laxity or an increased prevalence of patients in the 3 mm to 5 mm laxity group. Comparisons were repeated after the exclusion of the revision surgical procedures, but this did not affect the results.

Table 10.1. The correlation of IKDC scores and gender, use of the secondary tibial button fixation and revision.




Tibial button



84.5 ± 15.3

85.6 ± 16.0

81.6 ± 13

79.3 ± 19.8

74.0 ± 5.0

KT side to side (2yr)

1.25 ± 2.89

1.53 ± 2.25

1.67 ± 2.35*

1.00 ± 3.60

5.00 ± 2.00

The IKDC activity score represents a composite score of subjective questionnaires and clinical function. Activity in sedentary activities (activities of daily living), light activities (nonpivotal sports), moderate activities (tennis, skiing), and strenuous activity (jumping, pivoting sports) were graded by the patients. These subjective scores are combined with a mathematical formula to create the IKDC score. These scores were calculated at two years to be 84.5 ± 15.3 (Table 10.1). Age, gender, and meniscal pathology were not associated with a significant change in the IKDC score (Table 10.1 and Table 10.2). Patients with greater than 5 mm laxity were associated with a significantly decreased IKDC score from those with 0mm to 2mm or 3mm to 5mm (p > 0.02). There was also a trend toward a decreased score in patients with radiographic evidence of degenerative changes (p < 0.21).

Where BioScrew fixation was used in the case of a revision ACL in four cases, a 3 mm to 5 mm side-to-side difference was obtained in 3 cases, and a greater than 5 mm laxity was obtained in 1 case. Thus, in no case was an optimal mechanical result (<2mm) achieved. The significantly increased laxity (p < 0.005) in revision cases was also associated with a trend toward a decreased IKDC score with it averaging 74 in this group (p < 0.17).

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