Femoral Interference Screw Fixation in ACL Reconstruction Using Bone-Patellar Tendon-Bone Grafts

Femoral Fixation Strength as a Function of Bone Plug Length in Anterior Cruciate Ligament Reconstruction Utilizing Interference Screws

PURPOSE

 To determine femoral construct fixation strength as bone plug length decreases in anterior cruciate ligament reconstruction (ACLR).

METHODS

 Sixty fresh-frozen bone-patellar tendon-bone allografts were utilized and divided into 20-, 15-, and 10-mm length bone plug groups, subdivided further so that half utilized the patella side (P) for testing and half used the tibial side (T). Ten mm diameter recipient tunnels were created within the anatomic anterior cruciate ligament footprint of 60 cadaveric femurs. All bone plugs were 10 mm in diameter; grafts were fixed using a 7 × 23 mm metal interference screw. An Instron was used to determine the load to failure of each group. A one-way multivariate analysis of variance (MANOVA) was conducted to test the hypothesis that there would be one or more mean differences in fixation stability between 20- or 15-mm plug lengths (P or T) versus 10 mm T plug lengths when cross-compared, with no association between other P or T subgroups.

RESULTS

 The mean load to failure of the 20 mm plugs (20 P + T) was 457 ± 66N, 15 mm plugs (15 P + T) was 437 ± 74N, and 10 mm plugs (10 P + T) was 407 ± 107N. There was no significant difference between P + T groups: 20-versus 15-mm (p = 1.000), 15-versus 10-mm (p = 0.798), and 20-versus 10-mm (p = 0.200); P + T MANOVA (p = 0.291). Within groups, there was no significant difference between patella and tibial bone plug subgroups with a pullout force range between 469 ± 56N and 374 ± 116N and p-value ranging from p = 1.000 for longer bone plugs to p = 0.194 for shorter bone plugs; P versus T MANOVA (p = 0.113).

CONCLUSION

 In this human time zero cadaver model, there was no significant difference in construct failure between 20-,15-, and 10-mm bone plugs when fixed with an interference screw within the femoral tunnel, although fixation strength did trend down when from 20- to 15- to 10-mm bone plugs.

CLINICAL RELEVANCE

 There is a balance between optimal bone plug length on the femoral side for achieving adequate fixation as well as minimizing donor site morbidity and facilitating graft passage in ACLR. This study reveals utilizing shorter plugs with interference screw fixation is potentially acceptable on the femoral side if shorter plugs are harvested.

Smaller diameter femoral tunnel biocomposite interference screws provide adequate fixation strength in anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to evaluate the effect of bioabsorbable interference screw diameter on the pullout strength and failure mode for femoral tunnel fixation in primary anterior cruciate ligament reconstruction (ACLR) at time zero fixation using bone-patellar tendon-bone (BTB) autograft in a cadaveric model.

METHODS

Twenty-four fresh-frozen cadaveric knees were obtained from 17 different donors. Specimens were allocated to three different treatment groups (n = 8 per group) based on interference screw diameter: 6 mm, 7 mm, or 8 mm biocomposite interference screw. All specimens underwent dual energy X-ray absorptiometry (DEXA) scanning prior to allocation to ensure no difference in bone mineral density among groups (n.s.). All specimens underwent femoral-sided ACLR with BTB autograft. Specimens subsequently underwent mechanical testing under monotonic loading conditions to failure. The load to failure and failure mechanism were recorded.

RESULTS

The mean pullout force (N) at time zero for each group was 309 ± 213 N, 518 ± 313 N, and 541 ± 267 N for 6 mm, 7 mm, and 8 mm biocomposite interference screw diameter, respectively (n.s.). One specimen in the 6 mm group, two specimens in the 7 mm group, and one specimen in the 8 mm group failed by screw pullout. The remainder in each group failed by graft failure (n.s.).

CONCLUSION

Biocomposite interference screw diameter did not have a significant influence on fixation pullout strength or failure mode following femoral tunnel fixation using BTB autograft at time zero. A 6 mm interference screw can improve preservation of native bone stock, increase potential for biologic healing, and decrease the risk of damage to the graft during insertion without significantly compromising fixation strength. This study supports the use of smaller 6 mm interference screw diameter options for femoral tunnel fixation in ACLR.

Clinical and radiological comparison of bioactive glass and poly-L-lactic acid/hydroxyapatite bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament reconstruction

BACKGROUND

Ligament reconstruction is still the main treatment modality for patients with a complete ligament rupture. The semitendinosus tendon, alone quadrupled or double folded and combined with the gracilis tendon, is still the most frequently used autologous graft for a reconstructive procedure. Absorbable interference screw usage has gained popularity in the past decade because they create less artifacts during MR imaging and tend to osteointegrate over the years, arguably leading to a more anatomic fixation. The purpose of this study was to compare the 5-year radiological and clinical results of two different tibial graft fixation screws.

HYPOTHESIS

We hypothesized that bioabsorbable interference screws made of bioactive glass would lead to higher rates of osteointegration, better overall clinical results, less foreign body reaction rates and less tibial tunnel widening when compared to the poly-L-lactic acid/hydroxyapatite (PLLA-HA) screws.

PATIENTS AND METHODS

Fifty-one patients treated with an anatomic single bundle ACL reconstruction between June 2015 and July 2016 at our institution were included in the study. The tibial graft was fixed with a bioactive glass screw in 24, and with a PLLA-HA in 27 patients. Tibial tunnel widening, foreign body reaction, osteointegration and resorption rates were evaluated and compared on a magnetic resonance scan at a minimum of 5 year postoperatively. Overall clinical results and side-to-side difference on KT-1000 were also analyzed in-between groups.

RESULTS

Tibial tunnel widening was similar for both groups. Foreign body reaction, while not statistically significant, was less aggressive when bioactive glass screws were used. Osteointegration and resorption rates of the bioactive glass screws were significantly higher than the PLLA-HA group (p=0.000). While all patients showed an overall improvement on postoperative scores (p=0.000), patients with a bioactive glass interference screw had statistically higher translational stability with KT-1000, compared to the poly-L-lactic acid/hydroxyapatite group (p=0.001).

DISCUSSION

At a minimum of 5 years, compared to conventional PLLA-HA interference screws, 45S5 bioactive glass screw provide higher resorption rates, are more highly biodegradable and provide overall good clinical results.

LEVEL OF EVIDENCE

III.

Anterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon-Bone Allograft in Patients Aged 50 and Older Leads to Improved Activity Levels and Acceptable Patient-Reported Outcomes

PURPOSE

To evaluate patient-reported outcomes in patients aged 50 years and older undergoing anterior cruciate ligament reconstruction (ACLR) using bone-patellar tendon-bone (BPTB) allograft with minimum 2-year follow-up.

METHODS

A retrospective review was performed on a consecutive series of patients aged 50 and older who underwent ACLR using BPTB allograft by a single surgeon with minimum 2-year follow-up. Postoperative International Knee Documentation Committee (IKDC), Lysholm, and Physical Component Summary of the 12-item Short-Form Health Survey were used to assess outcomes, as well as preoperative and postoperative Tegner activity scores, which were compared using a paired sample t test.

RESULTS

Fifty patients met inclusion criteria, with a mean age of 55.3 ± 4.4 years and mean follow-up of 4.8 ± 1.9 years. Tegner activity scores improved from a mean preoperative score of 3.26 to a mean postoperative score of 5.25 (P < .001). The mean postoperative scores for Lysholm, IKDC, and Physical Component Summary were 87.3, 81.1, and 54.3, respectively. In total, 36 (72%) patients achieved a patient acceptable symptom state score for IKDC and 37 (74%) patients achieved a minimal clinically important difference for Tegner activity score. Thirty-eight (76%) patients reported good-to-excellent results, 6 (12%) patients reported fair results, and 6 (12%) patients reported poor results.

CONCLUSIONS

ACLR with BPTB allograft in patients aged 50 and older leads to good patient-reported outcomes with significantly increased postoperative activity status at a minimum 2-year follow-up.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.