Soft tissue tendon graft fixation in serially dilated or extraction-drilled tibial tunnels: a porcine model study using high-resolution quantitative computerized tomography

Synergistic Effect of Reverse Drilling and Bone Dust on Femoral Tendon-Bone Healing After Anterior Cruciate Ligament Reconstruction in a Rabbit Model

BACKGROUND

Anterior cruciate ligament (ACL) injuries and bone tunnel enlargement (BTE) after ACL reconstruction (ACLR) remain frequent issues. Bone dust (BD) produced by tunnel preparation with osteogenic ability and reverse drilling (RD), an easy compaction technique, make it accessible to enhance tendon-bone healing in the clinic.

HYPOTHESIS

RD and BD synergistically promote tendon-bone healing by improving peritunnel bone and preventing BTE in femurs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 96 New Zealand White rabbits underwent ACLR. The semitendinosus tendon was freed before medial parapatellar arthrotomy. After the native ACL was transected, bone tunnels were prepared through the footprint of the native ACL. All animals were randomly assigned to 1 of 4 groups according to different tunnel preparation methods: group 1 (irrigation after extraction drilling [ED]; control group), group 2 (irrigation after RD), group 3 (no irrigation after ED), and group 4 (no irrigation after RD). BD was harvested by irrigating tunnels and was characterized by morphology and size. The specimens underwent microarchitectural, histological, and biomechanical evaluations at 4, 8, and 12 weeks postoperatively.

RESULTS

Micro-computed tomography demonstrated more peritunnel bone and less BTE in the femurs of group 4 compared with the other groups. Histologically, BD possessed osteogenic activity in bone tunnels postoperatively. Meanwhile, group 4 regenerated a higher amount of the tendon-bone interface and more peritunnel bone than group 1. Biomechanically, group 4 showed higher failure loads and stiffness than group 1. However, peritunnel bone loss, active osteoclasts, and significant BTE were found in the femurs of group 1 and group 3 at 12 weeks postoperatively, while no strong correlation was found between BTE and inflammatory cytokines. Scanning electron microscopy and particle size analysis suggested that BD produced by ED and RD had no difference in size.

CONCLUSION

Tendon-bone healing was facilitated by the synergistic effect of RD and BD in femurs.

CLINICAL RELEVANCE

This study provides a more accessible and effective surgical strategy to promote tendon-bone healing after ACLR by increasing peritunnel bone and preventing BTE in femurs.

The Proximal Tibia Loses Bone Mineral Density After Anterior Cruciate Ligament Injury: Measurement Technique and Validation of a Quantitative Computed Tomography Method

Purpose

Results

Conclusions

Level of Evidence

Does a combined screw and dowel construct improve tibial fixation during anterior cruciate ligament reconstruction?

PURPOSE

The aims of the present study were to compare the biomechanical properties of tibial fixation in hamstring-graft ACL reconstruction using interference screw and a novel combination interference screw and dowel construct.

MATERIAL AND METHODS

We compared the fixation of 30 (2- and 4-stranded gracilis and semitendinosis tendons) in 15 fresh-frozen porcine tibiae with a biocomposite resorbable interference screw (Group 1) and a screw and dowel construct (Group 2). Each graft was subjected to load-to-failure testing (50 mm/min) to determine maximum load, displacement at failure and pullout strength.

RESULTS

There were no significant differences between the biomechanical properties of the constructs. Multivariate analysis demonstrated that combination constructs (β = 140.20, p = 0.043), screw diameter (β = 185, p = 0.006) and 4-strand grafts (β = 51, p = 0.050) were associated with a significant increase in load at failure. Larger screw diameter was associated with increased construct stiffness (β = 20.15, p = 0.020).

CONCLUSION

The screw and dowel construct led to significantly increased fixation properties compared to interference screws alone in a porcine model. Increased screw diameter and utilization of 4-strand ACL grafts also led to improvement in load-to-failure of the construct. However, this is an in vitro study and additional investigations are needed to determine whether the results are reproducible in vivo.

LEVEL OF EVIDENCE

Level V; Biomechanical study.

Does thread shape affect the fixation strength of the bioabsorbable interference screws for anterior cruciate ligament reconstructions? A biomechanical study

Background

The purpose of this study was to compare the biomechanical behaviour of two bioabsorbable interference screws with different geometries.

Methods

Two different pitch (2.5 and 5 mm) bioabsorbable interference screws, both 9 × 30 mm, were tested. Tests were performed with forty bovine digital extensor tendons and skeletally mature porcine tibiae. Two protocols of cyclic tests at 1 Hz were performed: 1000 cycles from 50 to 250 N, and 5000 cycles from 100 to 300 N (n = 10 for each type of test and screw). After the cyclic loading, a final ramp displacement until failure at 0.5 mm/s was applied.

Results

The stiffness after the cyclic phase of the tests was not statistically different between the two screws (1000th cycle: 2.5 mm pitch 280.3 ± 56.4 N/mm, 5 mm pitch 275.2 ± 65.0 N/mm, P = .965; 5000th cycle: 2.5 mm pitch 281.3 ± 66.4 N/mm, 5 mm pitch 286.1 ± 79.4 N/mm, P = .814). The yield load was not significantly different between the screws (1000 cycle tests: 2.5 mm pitch 482.2 ± 120.2 N, 5 mm pitch 495.9 ± 131.3 N, P = .508; 5000 cycle tests: 2.5 mm pitch 476.4 ± 65.3 N, 5 mm pitch 494.3 ± 39.2 N, P = .391). No correlation was found between the insertion torque and yield load (1000 cycle tests, R² = 0.013; 5000 cycle tests, R² = 0.006).

Conclusions

The pitch of bioabsorbable interference screws does not seem to affect fixation strength. Also, the authors recommend not to use insertion torque alone to estimate the fixation strength.

No Difference between Extraction Drilling and Serial Dilation for Tibial Tunnel Preparation in Anterior Cruciate Ligament Reconstruction: A Systematic Review

Importance

This review highlights a lack of consensus and need for further study regarding optimal tibial tunnel preparation method in anterior cruciate ligament reconstruction (ACLR).

Objective

This review examines existing clinical and biomechanical outcomes of both extraction drilling (ED) and serial dilation (SD) as a technique for tibial tunnel preparation in ACLR.

Evidence Review

In accordance with PRISMA guidelines, three electronic databases (MEDLINE, EMBASE, and PubMed) were searched and systematically screened in duplicate from database inception to September 6, 2017 for English-language, human studies, of all levels of evidence that examined ED and/or SD for tibial tunnel preparation in ACLR. Data including patient demographics, tibial tunnel preparation techniques, biomechanical and clinical outcomes and complications were retrieved from eligible studies.

Findings

ED was used in 71 patients, who were mean age 29.9 years (range: 17-50), 68% male, and followed for mean 16.5 months (range: 3.8-46). SD was used in 70 patients (70 knees), who were mean age 29.3 years (range: 18-50), 69% male, and followed for mean 14.1 months (range: 3.8-46). There were no statistically significant differences (mean preoperative; mean postoperative) for either tibial preparation technique for Lysholm (50.1; 92.5), Tegner (3.5; 6.1), International Knee Documentation Committee (IKDC) (48.8; 92.7), and Lachman or laxity scores. However, ED demonstrated statistically significant increased postoperative tibial tunnel expansion (1.8 mm versus 1.4 mm) and (at 12 weeks) graft migration at the tibial fixation site (1.3 mm versus 0.8 mm). Across biomechanical studies, there were no statistically significant differences (ED; SD) with forces required to initiate graft slippage (156 N; 174 N), graft stiffness (187 N; 186.5 N), and screw torque (1.6 N/m; 1.8 N/m). ED demonstrated a lower mean load to failure for the graft construct (433 N versus 631 N; p<0.05).

Conclusions and Relevance

Though biomechanical data demonstrated lower mean load to failure for the graft using ED, clinical data suggest increased tibial tunnel expansion and post-operative graft migration at the tibial fixation site. Future studies with long-term follow-up data are required to ascertain the optimal technique for graft incorporation and postoperative success.

Level of Evidence

IV:Systematic Review of Level I-IV studies.

Improvement of bone-tendon fixation by porous titanium interference screw: A rabbit animal model

The interference screw is a widely used fixation device in the anterior cruciate ligament (ACL) reconstruction surgeries. Despite the generally satisfactory results, problems of using interference screws were reported. By using additive manufacturing (AM) technology, we developed an innovative titanium alloy (Ti₆ Al₄ V) interference screw with rough surface and inter-connected porous structure designs to improve the bone-tendon fixation. An innovative Ti₆ Al₄ V interference screws were manufactured by AM technology. In vitro mechanical tests were performed to validate its mechanical properties. Twenty-seven New Zealand white rabbits were randomly divided into control and AM screw groups for biomechanical analyses and histological analysis at 4, 8, and 12 weeks postoperatively; while micro-CT analysis was performed at 12 weeks postoperatively. The biomechanical tests showed that the ultimate failure load in the AM interference screw group was significantly higher than that in the control group at all tested periods. These results were also compatible with the findings of micro-CT and histological analyses. In micro-CT analysis, the bone-screw gap was larger in the control group; while for the additive manufactured screw, the screw and bone growth was in close contact. In histological study, the bone-screw gaps were wider in the control group and were almost invisible in the AM screw group. The innovative AM interference screws with surface roughness and inter-connected porous architectures demonstrated better bone-tendon-implant integration, and resulted in stronger biomechanical characteristics when compared to traditional screws. These advantages can be transferred to future interference screw designs to improve their clinical performance. The AM interference screw could improve graft fixation and eventually result in better biomechanical performance of the bone-tendon-screw construct. The innovative AM interference screws can be transferred to future interference screw designs to improve the performance of implants. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2633-2640, 2018.

Screw oversizing for anterior cruciate ligament graft fixation in primary and enlarged tibial tunnels: A biomechanical study in a porcine model

BACKGROUND

Ideal diameter for tibial interference screw fixation of the anterior cruciate ligament (ACL) graft remains controversial. Tibial graft fixation with screws matching the tunnel diameter vs. one-millimetre oversized screws were compared.

METHODS

In 32 cadaveric porcine tibiae, bovine extensor tendons with a diameter of eight millimetres were fixed in (I) a primary ACL reconstruction scenario with eight-millimetre tibial tunnels (pACL), with eight-millimetre (pACL-8) vs. nine-millimetre (pACL-9) screws, and (II) a revision ACL reconstruction scenario with enlarged tunnels of 10 mm (rACL), with 10-mm (rACL-10) vs. 11-mm (rACL-11) screws. Specimens underwent cyclic loading with low and high load magnitudes followed by a load-to-failure test. Graft slippage and ultimate failure load were recorded.

RESULTS

In comparison with matched-sized screws (pACL-8), fixation with oversized screws (pACL-9) showed with significantly increased graft slippage during cyclic loading at higher load magnitudes (1.19 ± 0.23 vs. 1.98 ± 0.67 mm; P = 0.007). There were no significant differences between the two screw sizes in the revision scenario (rACL-10 vs. rACL-11; P = 0.38). Graft fixation in the revision scenario resulted in significantly increased graft slippage in comparison with fixation in primary tunnels at higher loads (pACL vs. rACL; P = 0.004). Pull-out strengths were comparable for both scenarios and all screw sizes (P > 0.316).

CONCLUSIONS

Matched-sized interference screws provided better ACL graft fixation in comparison with an oversized screw diameter. In revision cases, the fixation strength of interference screws in enlarged tunnels was inferior to the fixation strength in primary tunnels.

Can an expansion device be used in anterior cruciate ligament reconstruction? An in vitro study of soft tissue graft tibial fixation

BACKGROUND

The purpose of this study was to compare the mechanical properties of an interference screw with an expansion device in anterior cruciate ligament (ACL) reconstruction.

METHODS

A total of 52 porcine tibia and 20 polyurethane foam blocks (0.16g/cm³) were used. Forty pullout tests were carried out to combine the two types of bones - surrogate and porcine - with the two fixation systems: interference screw and expansion device (n=10 per group). Thirty-two cyclic tests (n=8 per group) were carried out with both fixation devices in porcine bone at two different force amplitudes (100N and 200N).

RESULTS

Stiffness and load values (mean±SD) at six millimeters of displacement for the expansion device and the interference screw were 74±33N/mm, 318±135N, and 52±28N/mm, 205±70N, respectively, showing a difference in stiffness (P=0.016) and load at six millimeters of displacement (P=0.001). No correlation between insertion torque and the ultimate failure load was found for both fixation devices tested. In cyclic tests, significantly higher (P<0.001) numbers of cycles (mean±SD) were reached with the expansion device (81,014±30,291 at 100N; 13,462±11,351 at 200N) than with the interference screw (15,100±8623 at 100N; 343±113 at 200N) at six millimeters of displacement.

CONCLUSION

The use of an expansion device for ACL reconstructions seemed to be a promising alternative to an interference screw. Insertion torque alone was not a useful predictor of graft fixation strength in ACL reconstructions.

In situ comparison of varying composite tibial tunnel interference screws used for ACL soft tissue graft fixation

PURPOSE

This mechanical study using an in vitro porcine model compared composite interference screw fixation of soft tissue ACL grafts in tibial tunnels.

METHODS

Forty-eight porcine profundus tendons and tibiae were divided into four groups of 12 closely matched specimens. Equivalent diameter grafts were assigned to each group. Tibial bone tunnels were drilled to 0.5mm greater than graft diameter. Grafts were fixed in tunnels using one 10 × 35 mm composite interference screw designed by four different manufacturers. Maximal insertion torque and perceived within group mechanical testing outcome predictions were recorded. Constructs were potted and loaded into a six degrees of freedom clamp that placed the servohydraulic device tensile loading vector in direct tunnel alignment. Constructs were pre-loaded to 25 N, pre-conditioned between 0 and 50 N for 10 cycles (0.5 Hz), submaximally tested between 50 and 250 N for 500 cycles (one hertz) and load to failure tested at 20mm/min.

RESULTS

Statistically significant differences were not observed between groups for displacement during submaximal cyclic loading, yield load, displacement at yield load, stiffness, ultimate load at failure and displacement at ultimate load. One composite screw group displayed a slightly greater proportion of specimens that required use of more than one screw during insertion.

CONCLUSIONS

Under highly controlled conditions groups displayed comparable fixation.

ACL double bundle linked cortical-aperture tibial fixation: a technical note

INTRODUCTION

The purpose of this technical note is to describe the tibial fixation characteristics for an all-inside anatomic anterior cruciate ligament (ACL) reconstruction method that links extra-cortical button suspensory and aperture fixation replicating double bundle soft tissue graft function in single femoral and tibial sockets.

MATERIALS AND METHODS

A 55° drill guide aligned guidewires in the ACL footprint center of 8 porcine tibiae (mean apparent bone mineral density = 1.15 g/cm(2)). A Flipcutter created 27 mm sockets and 15 mm guidewire channels. Advancement sutures seated porcine soft tissue graft-PEEK implants to achieve both socket aperture and extra-cortical button suspensory fixation. Potted specimens were loaded into a 6º of freedom clamp with the servohydraulic loading vector in direct socket alignment. Constructs were pre-loaded to 25 N, underwent 10 pre-conditioning cycles (0-50 N, 0.5 Hz), and 500 submaximal loading cycles (50-250 N, 1 Hz) prior to load to failure testing (20 mm/min). Mode of failure was recorded. Descriptive statistical analysis was performed.

RESULTS

All specimens survived the biomechanical test protocol. Displacement during cyclic loading was 2.8 ± 0.9 mm, yield load was 475.2 ± 36 N, ultimate load at failure was 671.4 ± 98 N, stiffness was 127.5 ± 15 N/mm. The most common failure mode was suture pulling through the soft tissue graft.

CONCLUSIONS

This ACL reconstruction method combines the high ultimate load to failure and low graft slippage of extra-cortical button suspensory fixation with the high stiffness of aperture fixation. Biomechanical test findings were comparable or better to previous reports for displacement during submaximal loading, ultimate failure load, and construct stiffness. Based on current understanding of soft tissue graft ACL reconstruction biomechanics, this fixation method should enhance graft-bone socket integration during healing, facilitate long-term graft survival, and improve patient outcomes. Clinical studies are needed to confirm in vivo efficacy.

Comparison of Pull-out Strength for Different Bone Block Length in a Porcine Anterior Cruciate Ligament Model

Background:

Bone block length for bone–patellar tendon–bone (BPTB) anterior cruciate ligament (ACL) reconstruction has traditionally been 25 mm in length. The previous surgical technique did not require the surgeon to pay particular attention to the length of the bone block, and therefore, there is scant evidence in the literature describing ideal lengths. With the gaining popularity of accessory medial portal drilling of the femoral tunnel, concerns with tunnel length and graft shuttling have surfaced. Newer techniques have advised shortening of the femoral bone block to accommodate the shorter tunnel and for ease of bone block manipulation into the aperture of the tunnel.

Purpose:

To compare the effects of bone block length on the pull-out strength of patellar tendon grafts using metal interference screws in a porcine ACL reconstruction model. The hypothesis was that the pull-out strength of each length of bone block under cyclic and ultimate load to failure testing would surpass the physiologic loads experienced by a normal ACL.

Study Design:

Controlled laboratory study.

Methods:

This study used 27 unmatched porcine femurs and BPTB constructs. Specimens were randomly assigned to a 10-, 15-, or 20-mm bone block reconstruction and a cycle load of 100, 500, or 1000 cycles. This resulted in 9 specimen groups with 3 specimens in each group. A central composite design (CCD) for the test matrix was selected, as this was optimum for requiring relatively few experiments while still exploring the complete range of interest for 2 independent variables. Each reconstruction used a 7 × 20–mm titanium interference screw. All reconstructions were performed on the femoral side using 10-mm-wide patellar tendon grafts, and tensile tests were performed. The loading protocol started with a 20-N preload, then cyclic testing to the appropriate number of cycles in the elastic region between 50 and 150 N at a strain rate of 200 mm/min, and then ended with ultimate load-to-failure testing. Ultimate load to failure, peak stress, elongation, and stiffness were all recorded. The patellar tendon graft mode of failure was measured by visual inspection.

Results:

During load-to-failure testing, 5 of 9 graft constructs in the 10-mm group failed at the bone block, while 2 of 9 failed in the 15-mm group at this interface. In the 20-mm group, all 9 specimens failed at the tendon, and none failed at the bone block. There was a statistically significant difference in modes of failure between the bone block length groups in the reconstructed ACL grafts. Analysis indicates that a smaller bone block length graft is more likely to fail due to a bone block failure than a tendon failure. The average ± standard deviation failure load for all specimens was 573 ± 171 N. The mean failure loads for the 10-, 15-, and 20-mm groups were 614 ± 110, 658 ± 92, and 540 ± 203 N, respectively. There was no statistical significance between the groups in any of these measurements.

Conclusion:

Bone blocks of 20 to 25 mm in length are normally used in surgical practice. Thus, the purpose of this study was to explore the effects of a smaller bone block length in the fixation strength of a graft. This study could not yield a significant difference in failure load for differently sized bone blocks. There was a significant tendency of shorter bone block lengths to fail due to bone block failure.

Clinical Relevance:

Bone block failure was defined as slippage of the bone block or interference screw. These results show that using a smaller bone block may increase the likelihood of a graft failure in an ACL reconstruction.

Biomechanical comparison of interference screws and combination screw and sheath devices for soft tissue anterior cruciate ligament reconstruction on the tibial side

BACKGROUND

The tibial fixation site has been reported to be the weakest point in anterior cruciate ligament (ACL) reconstructions. Numerous interference screws and combination screw and sheath devices are available for soft tissue fixation, and a biomechanical comparison of these devices is necessary.

HYPOTHESIS

Combination screw and sheath devices would provide superior soft tissue fixation properties compared with interference screws in a porcine model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight different intratunnel tibial soft tissue fixation devices were biomechanically tested in a porcine model with bovine tendons, with 10 specimens per group. The soft tissue fixation devices included 3 interference screws-the Bio-Interference Screw, BIOSURE PK, and RCI Screw-and 5 combination screw and sheath devices (combination devices)-the AperFix II, BIOSURE SYNC, ExoShape, GraftBolt, and INTRAFIX. The specimens were subjected to cyclic (1000 cycles, 50-250 N, 0.5 Hz) and pull-to-failure loading (50 mm/min) with a dynamic tensile testing machine. Ultimate failure load (N), cyclic displacement (mm), pull-out stiffness (N/mm), displacement at failure (mm), load at 3 mm displacement (N), and mechanism of failure were recorded.

RESULTS

The ultimate failure loads were highest for the GraftBolt (1136 ± 115.6 N), followed by the INTRAFIX (1127 ± 155.0 N), AperFix II (1122 ± 182.9 N), BIOSURE PK (990.8 ± 182.1 N), Bio-Interference Screw (973.3 ± 95.82 N), BIOSURE SYNC (829.5 ± 172.4 N), RCI Screw (817.7 ± 113.9 N), and ExoShape (814.7 ± 178.8 N). The AperFix II, GraftBolt, and INTRAFIX devices were significantly stronger than the BIOSURE SYNC, RCI Screw, and ExoShape. Although the 3 strongest devices were combination screw and sheath devices, no significant differences were observed between the ultimate failure strengths of the screw and combination devices when compared as groups. The least amount of cyclic displacement after 1000 cycles was observed for the GraftBolt (1.38 ± 0.27 mm), followed by the AperFix II (1.58 ± 0.21 mm), Bio-Interference Screw (1.61 ± 0.22 mm), INTRAFIX (1.63 ± 0.15 mm), ExoShape (1.68 ± 0.30 mm), BIOSURE PK (1.72 ± 0.29 mm), BIOSURE SYNC (1.92 ± 0.59 mm), and RCI Screw (1.97 ± 0.39 mm). The GraftBolt allowed significantly less displacement than did the BIOSURE SYNC and RCI Screw. Similarly, no significant differences were observed between the cyclic displacements of the screws and combination devices when compared as groups.

CONCLUSION

The combination screw and sheath devices did not provide superior soft tissue fixation properties compared with the interference screws alone in a porcine model. Although the highest ultimate failure loads and least amounts of cyclic displacement were observed for combination devices, group comparisons of screw and combination devices did not result in any significant differences for ultimate failure load and cyclic displacement.

CLINICAL RELEVANCE

It is important to consider that these results represent device performance in an in vitro animal model and are not directly transferrable to an in vivo clinical situation. The combination of a sheath and screw did not consistently result in improved fixation characteristics compared with interference screw fixation.

Measurement of bone mineral density in the tunnel regions for anterior cruciate ligament reconstruction by dual-energy X-ray absorptiometry, computed tomography scan, and the immersion technique based on Archimedes' principle

PURPOSE

To determine, for anterior cruciate ligament (ACL) reconstruction, whether the bone mineral density (BMD) of the femoral tunnel was higher than that of the tibial tunnel, to provide objective evidence for choosing the appropriate diameter of interference screws.

METHODS

Two groups were enrolled. One group comprised 30 normal volunteers, and the other comprised 9 patients with ACL rupture. Dual-energy X-ray absorptiometry was used to measure the BMD of the femoral and tibial tunnel regions of the volunteers' right knees by choosing a circular area covering the screw fixation region. The knees were also scanned by spiral computed tomography (CT), and the 3-dimensional reconstruction technique was used to determine the circular sections passing through the longitudinal axis of the femoral and tibial tunnels. Grayscale CT values of the cross-sectional area were measured. Cylindrical cancellous bone blocks were removed from the femoral and tibial tunnels during the ACL reconstruction for the patients. The volumetric BMD of the bone blocks was measured using a standardized immersion technique according to Archimedes' principle.

RESULTS

As measured by dual-energy X-ray absorptiometry, the BMD of the femoral and tibial tunnel regions was 1.162 ± 0.034 g/cm(2) and 0.814 ± 0.038 g/cm(2), respectively (P < .01). The CT value of the femoral tunnel region was 211.7 ± 11.5 Hounsfield units, and the value of the tibial tunnel region was 104.9 ± 7.4 Hounsfield units (P < .01). The volumetric BMD of the bone block from the femoral tunnel (2.80 ± 0.88 g/cm(3)) was higher than the value from the tibial tunnel (1.88 ± 0.59 g/cm(3)) (P < .01). Comparing the data between male and female patients, we found no significant difference in both femoral and tibial tunnel regions.

CONCLUSIONS

For ACL reconstruction, the BMD of the femoral tunnel is higher than that of the tibial tunnel. This implies that a proportionally larger-diameter interference screw should be used for fixation in the proximal tibia than that used for fixation in the distal femur.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Serial dilation reduces graft slippage compared to extraction drilling in anterior cruciate ligament reconstruction: a randomized controlled trial using radiostereometric analysis

PURPOSE

This study tested the hypothesis that serial dilation of the tibial tunnel could provide a stronger anchorage of the graft-fixation-device complex compared to traditional extraction drilling.

METHODS

Forty patients (22 men and 18 women) undergoing ACL reconstruction were randomized to either extraction drilling (group ED) or compaction by serial dilation (group SD) of the tibial tunnel. Tantalum beads were placed in the tibia, femur, and in the hamstring graft. Radiostereometric analysis (RSA) was performed postoperatively and again after 6, 12, and 24 weeks. Migration of graft in the bone tunnels as well as knee laxity was assessed using RSA and a TELOS stress device.

RESULTS

Six patients (three men and three women) were excluded during follow-up, which resulted in 17 patients in group ED [median age 30 years (range 20-50)] and 17 patients in group SD [median age 32 years (range 20-49)]. The mean migration of the graft in the tibial bone canal after 3 months was 1.3 (SD 0.6) mm in group ED and 0.8 (SD 0.5) mm in group SD (P = 0.02). The overall knee laxity after 3 months was 13.0 (SD 4.0) mm in group ED and 10.9 (SD 3.1) mm in group SD.

CONCLUSION

This study found less slippage of the hamstring graft in the tibial bone canal in the serial dilated group compared to the extraction drilling group. The clinical relevance of the difference is unknown. No difference in stress radiographic knee laxity was found between the two groups.

Fixation strength of the interference screw in the femoral tunnel: The effect of screw divergence on the coronal plane

Clinical studies to examine the effect of screw divergence have not been applied to the fixation of hamstring grafts. A few previous reports have addressed the correlations between the loss of pullout strength and divergence on hamstring tendon fixation in biomechanical tests. The purpose of this study was to examine the effect of interference screw divergence on the coronal plane when digital flexor tendons were fixed with an interference screw. Twenty fresh porcine hindlimb specimens were chosen. The grafts were fixed using titanium soft tissue interference screws. The hindlimbs were divided into two groups according to the insertion method of the screw. The screw was placed along the graft parallel to the long axis of the femoral tunnel in 10 specimens (parallel placement group), and the others were placed laterally at a 15° divergent angle from the bone tunnel on the coronal plane (divergence group). The cyclic-loading test was loaded for 1500cycles. Five specimens failed because of a pull-out of the tendon in divergence group. The number of specimens that failed before the completion of cycles in the divergence group was significantly greater than that in the parallel placement group. Although the residual displacement after 1500cycles for the divergence group was greater than that for the parallel placement group, no statistically significant difference was found between the groups. This study suggests that the screw placed laterally at a 15° divergent angle on the coronal plane decreases the fixation strength of the digital flexor tendons fixed with an interference screw.

Biceps tenodesis with interference screw: cyclic testing of different techniques

Different surgical techniques exist for biceps tenodesis. The most secure fixation technique is with interference screws. The purpose of the study was to compare the biomechanical performance of three different interference screw biceps tenodesis fixation methods, which involve different tunnel preparation methods. Using a sheep shoulder model and metal interference screws, a bone wedge technique was compared to serial tunnel dilation and a control group. After a preload, all repairs were cyclically loaded (20-60 N) for 100 cycles followed by destructive testing. Biceps tenodesis using an interference screw--bone wedge technique showed statistically lower cyclic displacement (8.1 ± 6.4 mm) than serial dilatation with an interference screw (21.3 ± 8.4 mm) or interference screw fixation alone (18.3 ± 8.3 mm) (P = 0.02). There were no statistically significant differences in ultimate failure strength for any of the interference screw biceps tenodesis techniques tested. The tunnel preparation method chosen for interference screw fixed biceps tenodesis can have a positive effect on tenodesis performance. Using the bone wedge technique may allow a more rapid rehabilitation program applicable for the traumatic biceps tendon rupture seen in young, athletic patients with high demands.

Serial dilation versus extraction drilling in anterior cruciate ligament reconstruction: a biomechanical study

The hamstring tendon graft has become increasingly popular in anterior cruciate ligament reconstruction because of low donor-site morbidity. However, the tibial fixation is considered difficult, mainly because of low tibial mineral bone density. Therefore, we tested whether preparation of the tibial tunnel with compaction by serial dilation provided a stronger anchorage of the graft-fixation-device complex than does traditional extraction drilling of the tibial tunnel. In 20 bovine tibiae, the bone tunnels were created with either extraction drilling (group 1) or compaction by serial dilation (group 2). Twenty bovine digital extensor tendons were fixated in the bone tunnel with an Intrafix tibial fastener. The graft-fixation-device complexes were mounted in a hydraulic test machine. The fixation strength was evaluated after cyclic loading. The difference between the serial dilation group and the extraction drilling group ranged from a mean slippage of 0 mm at 70-220 N, to a mean slippage of 0.1 mm at 70-520 N. We found no significant difference in slippage of the graft-fixation-device complex after 1,600 cycles. This study failed to show a significant difference between compaction by serial dilation and extraction drilling of the tibia bone tunnel in anterior cruciate ligament reconstruction.

Use of co-registered high-resolution computed tomography scans before and after screw insertion as a novel technique for bone mineral density determination along screw trajectory

INTRODUCTION

Bone mineral density (BMD) is an important factor in the examination of the performance of bone instrumentation both in and ex vivo, and until now, there has not existed a reliable technique for determining BMD at the precise location of such hardware. This paper describes such a technique, using cadaveric human sacra as a model.

METHODS

Nine fresh-frozen sacra had solid and hollow titanium screws placed into the S1 pedicles from a posterior approach. High-resolution micro-computed tomography (CT) was performed on each specimen before and after screw placement. All images were reconstructed with an isotropic spatial resolution of 308 mum, reoriented, and the pre-screw and post-screw scans were registered and transformed using a six-degree rigid-body transformation matrix. Once registered, two points, corresponding to the center of the screw at the cortex and at the screw tip, were determined in each scan. These points were used to generate cylindrical regions of interest (ROI) with the same trajectory and dimensions as the screw. BMD measurements were obtained within each of the ROI in the pre-screw scan. To examine the effect of artefact on BMD measurements around the titanium screws, annular ROI of 1 mm thickness were created expanding from the surface of the screws, and BMD was measured within each in both the pre- and post-screw scans.

RESULTS

The registration process was accurate to 190 mum, with a precision of 189 mum and error in BMD measurement of +/-2% in repeated scans. BMD values in the cylindrical ROI corresponding to screw trajectories were not statistically different from side to side of each specimen (p=0.23). Metal artefact created significant differences in BMD values (p=0.001) and followed an exponential decay curve as distance from the screws increased, approaching a low value of approximately 20 mg HA cm(-3), but not disappearing completely.

SUMMARY

CT in the presence of metal creates artefact, making measured BMD values near implants unreliable. This technique is accurate for determination of BMD, non-destructive, and eliminates the problem of this metal artefact through the use of co-registered scans. This technique has applications both in vitro and in vivo.

Tibial fixation of bone-patellar tendon-bone grafts in anterior cruciate ligament reconstruction: a cadaveric study of bovine bone screw and biodegradable interference screw

BACKGROUND

The use of interference screw fixation for bone-patellar tendon-bone grafts in anterior cruciate ligament fixation is well established. No previous study has compared bovine bone screws and biodegradable interference screws or demonstrated their efficacy for requirements associated with early rehabilitation.

HYPOTHESIS

There is no difference in tension loss and pull-out strength between bovine bone screws and biodegradable interference screws.

STUDY DESIGN

Controlled laboratory study.

METHODS

Anterior cruciate ligament reconstructions with bone-patellar tendon-bone allografts were performed in 40 human tibiae from 20 donors. A bovine bone screw and a polylevolactide interference screw were used for tibial fixation in each pair. A cyclic testing protocol with varying magnitude and orientation of the graft loading was developed. Cyclic tests were performed at 1 Hz for 5000 cycles with a peak force of 200 N applied to the graft. Survival rate and postcyclic-test pull-out strength were compared.

RESULTS

Fifteen of 20 reconstructions fixed with bovine bone screws and 17 of 20 fixed with biodegradable screws reached 5000 cycles. Graft tension drop after the 5000 cycles averaged 19.7 N ( +/- 12.9) for bovine bone screws and 18.9 N ( +/- 16.3) for biodegradable screws. There were no significant differences in tension loss and pull-out strength between the 2 types of screws.

CONCLUSION

Bovine bone screws are comparable to biodegradable interference screws in providing stable tibial fixation in anterior cruciate ligament reconstruction using bone-patellar tendon-bone allografts.

CLINICAL RELEVANCE

The use of bovine bone screws may be comparable to the popular biodegradable interference screws used for anterior cruciate ligament reconstruction in postsurgery rehabilitation.

Biomechanical comparison between CentraLoc and Intrafix fixation of quadrupled semitendinosus-gracilis allografts in cadaveric tibiae with low bone mineral density

Supplementary or back-up tibial tunnel fixation of a quadruple semitendinosus-gracilis (STG) graft is often performed when the knee surgeon questions the integrity of intra-tunnel fixation. Back-up fixation devices such as staples however may contribute to increased knee pain and dysfunction. Both primary extra-tunnel and intra-tunnel fixation devices may provide sufficient quadruple STG graft fixation in a tibial tunnel to preclude the need for back-up fixation. This biomechanical study compared the fixation of quadruple STG allografts in standard drilled tunnels prepared in low apparent bone mineral density (BMD) cadaveric tibiae using either an Intrafix device with primary intra-tunnel fixation in a region of predominantly cancellous trabecular bone, or a CentraLoc device with primary extra-tunnel fixation in a region of predominantly cortical bone. The study hypothesis was that the CentraLoc device would display superior fixation in these low apparent BMD cadaveric tibiae. Matched pair tibiae and quadruple STG allografts were divided into two groups of seven specimens each. Extraction drilled tunnels matched allograft diameter. Constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles and isometric pretensioned at 50 N for 1 min prior to undergoing 500 loading cycles (50-250 N) and load to failure testing (20 mm/min). The CentraLoc group displayed superior load at failure (448.4+/-171 N vs. 338.4+/-119 N, P=0.04) and survived more loading cycles (410+/-154 cycles vs. 196+/-230 cycles, P=0.04) than the Intrafix group. Most CentraLoc group specimens (6/7, 85.7%) failed by device pullout with intact quadruple STG allograft strands while all Intrafix group specimens (7/7, 100%) failed by slippage of one or more strands (P=0.005).