A technique for resolution of graft-tunnel length mismatch in central third bone-patellar tendon-bone anterior cruciate ligament reconstruction

Six Percent Incidence of Graft-Tunnel Mismatch in Anatomic Anterior Cruciate Ligament Reconstruction Using Bone-Patella Tendon-Bone Autograft and Anteromedial Portal Drilling

Purpose

The purpose of this study was to determine the incidence of graft-tunnel mismatch (GTM) when performing anatomic anterior cruciate ligament reconstruction (ACLR) using bone-patella tendon-bone (BPTB) grafts and anteromedial portal drilling.

Methods

Beginning in November 2018, 100 consecutive patients who underwent ACLR by two sports fellowship-trained, orthopedic surgeons using BPTB autograft and anteromedial portal drilling were prospectively identified. The BPTB graft dimensions and the femoral tunnel distance, tibial tunnel distance, intra-articular distance, and total distance were measured. Surgeons determined the depth and angle of tunnels based on the patella tendon graft length dimensions in each case. After passage of the graft, the distance from the distal graft tip to the tibial cortex aperture was measured. GTM was defined as the need for additional measures to obtain satisfactory tibial graft fixation (<15–20 mm of bone fixation).

Results

The incidence of mismatch was 6/100 (6%). Five cases involved the graft being too long, with the tibial bone plug protruding excessively from the tibial tunnel—4/5 had a patella tendon length ≥ 50 mm. Three cases were managed with femoral tunnel recession, and two were treated with a free bone plug technique. One patient with a patella tendon length of 35 mm had a graft that was too short, with the tibial bone plug recessed in the tibial tunnel. Of patients whose tibial tunnel distance was within 5 mm of the patella tendon length, only 1/46 (2%) patients had mismatch, whereas 5/54 (9%) of patients who had >5 mm difference had mismatch.

Conclusions

The incidence of graft-tunnel mismatch after anatomic ACLR using BTPB and anteromedial portal drilling in this study is 6%. To limit the occurrence of GTM where the graft is too long, surgeons should drill tibial tunnel distances within 5 mm of the patella tendon length.

Clinical Relevance

The results of this study provide surgeons with a technique of limiting graft tunnel mismatch when performing ACLR using BPTB and anteromedial portal drilling.

Blumensaat Line as a Prediction of Native Anterior Cruciate Ligament Length

Background:

Graft-tunnel mismatch (GTM) is a condition in which the anterior cruciate ligament (ACL) graft is either too long or too short. GTM is particularly problematic when bone–patellar tendon–bone grafts are used because of a potential compromise in fixation of the bone plug on the tibia.

Hypothesis:

The Blumensaat line (BL), a radiographic landmark representing the roof of the intercondylar fossa, will accurately approximate the native ACL (nACL) length and may aid in the prevention of GTM.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

A total of 130 patients (66 males, 64 females) underwent direct measurement of the nACL during knee arthroscopy. The lengths of the nACL and patellar ligament (PL) were measured intraoperatively, and BL length was measured on lateral knee radiographs. The nACL length was compared with PL and BL lengths to calculate the absolute difference (AD). Mean AD was calculated and used to determine mean percentage difference (MPD). Pearson correlation coefficients (CC) between BL, PL, and nACL length were calculated, along with inter- and intraobserver reliability coefficients for the measurement of BL.

Results:

For male patients, the mean length of the nACL was 32.5 mm, BL was 30.4 mm, and PL was 49.2 mm. The AD between the BL and nACL was 2.4 ± 1.3 mm, MPD was 2.6% ± 1.9%, and CC was 0.88. The CC between the PL and nACL was 0.08. For female patients, the mean length of the nACL was 30.2 mm, BL was 27.5 mm, and PL was 44.4 mm. The AD between the BL and nACL was 2.7 ± 1.7 mm, MPD was 4.5% ± 2.4%, and CC was 0.93. The CC between the PL and nACL was 0.1. The inter- and intraobserver reliability coefficients for the measurement of BL were 0.86 and 0.83, respectively.

Conclusion:

A strong correlation was found between BL and nACL with a high inter- and intraobserver reliability. This correlation provides a simple and reliable method to closely approximate nACL length before reconstruction and may aid in the prevention of graft-tunnel mismatch.

How to Avoid Graft-Tunnel Length Mismatch in Modified Transtibial Technique for Anterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon-Bone Graft

Background

We conducted this study to determine the optimal length of patellar and tibial bone blocks for the modified transtibial (TT) technique in anterior cruciate ligament (ACL) reconstruction using the bone-patellar tendon-bone (BPTB) graft.

Methods

The current single-center, retrospective study was conducted in a total of 64 patients with an ACL tear who underwent surgery at our medical institution between March 2015 and February 2016. After harvesting the BPTB graft, we measured its length and that of the patellar tendon, patellar bone block, and tibial bone block using the arthroscopic ruler and double-checked measurements using a length gauge. Outcome measures included the length of tibial and femoral tunnels, inter-tunnel distance, length of the BPTB graft, patellar tendon, patellar bone block, and tibial bone block and graft-tunnel length mismatch. The total length of tunnels was defined as the sum of the length of the tibial tunnel, inter-tunnel distance and length of the femoral tunnel. Furthermore, the optimal length of the bone block was calculated as (the total length of tunnels - the length of the patellar tendon) / 2. We analyzed correlations of outcome measures with the height and body mass index of the patients.

Results

There were 44 males (68.7%) and 20 females (31.3%) with a mean age of 31.8 years (range, 17 to 65 years). ACL reconstruction was performed on the left knee in 34 patients (53%) and on the right knee in 30 patients (47%). The optimal length of bone block was 21.7 mm (range, 19.5 to 23.5 mm). When the length of femoral tunnel was assumed as 25 mm and 30 mm, the optimal length of bone block was calculated as 19.6 mm (range, 17 to 21.5 mm) and 22.1 mm (range, 19.5 to 24 mm), respectively. On linear regression analysis, patients' height had a significant correlation with the length of tibial tunnel (p = 0.003), inter-tunnel distance (p = 0.014), and length of patellar tendon (p < 0.001).

Conclusions

Our results indicate that it would be mandatory to determine the optimal length of tibial tunnel in the modified TT technique for ACL reconstruction using the BPTB graft. Further large-scale, multi-center studies are warranted to establish our results.

Minimizing Graft-Tunnel Mismatch in Allograft Anterior Cruciate Ligament Reconstruction Using Blumensaat's Line: A Cadaveric Study

PURPOSE

To evaluate the accuracy of Blumensaat's line (BL) in predicting the tendinous graft length and tibial tunnel length (TTL) in an independent-tunnel anterior cruciate ligament reconstruction (ACLR) using a bone-patellar tendon-bone (BTB) allograft.

METHODS

Eighteen ACLRs were performed on cadaveric specimens using an anteromedial portal technique. All knees had no previous surgeries or deformities. Lateral knee radiographs of each specimen were taken prior to the ACLR, and BL was measured. Length-specific allografts for the tendinous portion of the grafts were then ordered by adding 20 mm to the length of BL. The TTL was predicted by subtracting BL and femoral tunnel length (FTL) from the overall graft length. Graft-tunnel mismatch (GTM) was recorded for each specimen. Statistical analysis compared overall results with the gold standard (0 mm) of GTM.

RESULTS

The average lateral femoral condyle width measured in line with the femoral tunnel was 33 ± 3.43 mm. The average FTL was 25 ± 0.54 mm. The average intra-articular distance (IAD) between femoral and tibial tunnel apertures was 31 ± 3.65 mm. The average TTL was 35 ± 2.21 mm. The difference between the predicted TTL and the actual TTL was not statistically significant (P = .3). The mean GTM was -0.9 ± 3.15 mm. There was no statistically significant difference between the BL method and the gold standard (P = .45). The mean percent difference between BL and the IAD was 5.2%.

CONCLUSIONS

The BL method can accurately predict the desired length for the tendinous portion of a BTB allograft as well as the TTL, thereby potentially minimizing GTM during arthroscopic BTB allograft ACLR. Patient-specific allografts can be ordered preoperatively based on BL.

CLINICAL RELEVANCE

This method provides the surgeon a way to avoid GTM preoperatively by ordering patient-specific grafts prior to performing an independent-tunnel BTB allograft ACLR.

The biomechanical effects of graft rotation on ACL reconstruction tunnel mismatch

PURPOSE

Bone block protrusion out of the tibial tunnel due to a relatively long graft is a common complication in anterior cruciate ligament surgical reconstruction with a patellar tendon. One possible solution is to shorten the patellar tendon graft already fixed in the femur by applying external rotation. This study aimed to evaluate the degree of shortening and biomechanical changes in porcine patellar grafts subjected to relatively higher degrees of rotation. Data obtained with rotations of 0°, 540°, 720°, and 900° were compared.

METHODS

Forty patellar porcine ligaments were subjected to biomechanical tests of degree of shortening, modulus of elasticity and maximum tension in the tendon before rupture. Tests were conducted using a universal mechanical testing machine and a computerized system for acquiring strength and deformation data.

RESULTS

Progressive shortening of the patellar ligament occurred with rotations of 0°, 540° and 720°. However, the degree of shortening showed no statistically significant difference as rotation increased from 720° to 900°. Decreased modulus of elasticity was observed compared with the graft rotation at 0° in all groups tested, but no statistically significant differences were observed among 540°, 720° and 900°. The maximum tension of the patellar tendon showed no change before rupture, regardless of the degree of rotation.

CONCLUSIONS

Rotating the patellar tendon is an efficient method for shortening a relatively long graft; however, more biomechanical studies are necessary to recommend this technique in clinical practice owing to the resulting decrease in graft stiffness that could compromise knee stability.

A Comparative Study on the Postoperative Outcomes of Anterior Cruciate Ligament Reconstruction Using Patellar Bone-Tendon Autografts and Bone-Patellar Tendon-Bone Autografts

PURPOSE

To evaluate and compare the clinical outcomes of anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BPTB) autograft and a patellar bone-tendon (PBT) autograft.

METHODS

Seventy-nine patients who underwent ACL reconstruction using either a BPTB autograft or a PBT autograft were retrospectively evaluated. The minimum follow-up period was 24 months after surgery. A graft selection was determined by the patellar tendon length as measured on preoperative magnetic resonance imaging. If the patellar tendon length was longer than or equal to 45 mm, a PBT graft attached with the EndoPearl device was used. Fifty-one patients used BPTB autografts (group B) and 28 patients used PBT autografts (group P). The Lachman test, pivot-shift test, and anterior translation tested with a KT2000 arthrometer were assessed. Functional outcomes were assessed with the use of the Lysholm score, International Knee Documentation Committee subjective score, and objective grade. Anterior knee pain including kneeling pain was assessed with the use of the Shelbourne and Trumper questionnaire.

RESULTS

There was no statistically significant difference between the 2 groups in the postoperative values of degree of anterior translation (P = .76), Lysholm score (P = .62), International Knee Documentation Committee subjective score (P = .91), and objective grade (P = .91). However, anterior knee pain assessed with the use of the Shelbourne and Trumper questionnaire (group B = 90 [range, 65 to 100], group P = 95 [range, 59 to 100], P = .02) and number of patients having kneeling pain (group B = 41%, group P = 18%, P = .04) differed significantly between the 2 groups.

CONCLUSIONS

ACL reconstruction using a PBT autograft provided reliable knee stability comparable to a BPTB autograft but with less kneeling pain. For patients who have a long patellar tendon that may cause graft-tunnel mismatch, a PBT can be an effective alternative graft option for arthroscopic ACL reconstruction.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Is the native ACL insertion site "completely restored" using an individualized approach to single-bundle ACL-R?

PURPOSE

The goal of individualized anatomic anterior cruciate ligament reconstruction (ACL-R) is to reproduce each patient's native insertion site as closely as possible. The amount of the native insertion site that is recreated by the tunnel aperture area is currently unknown, as are the implications of the degree of coverage. As such, the goals of this study are to determine whether individualized anatomic ACL-R techniques can maximally fill the native insertion site and to attempt to establish a crude measure to evaluate the percentage of reconstructed area as a first step towards elucidating the implications of complete footprint restoration.

METHODS

This is a prospective pilot study of 45 patients who underwent primary single-bundle anatomic ACL-R from May 2011 to April 2012. Length and width of the native insertion site were measured intraoperatively. Using published guidelines, reconstruction technique and graft choice were determined to maximize the percentage of reconstructed area. Native femoral and tibial insertion site area and femoral tunnel aperture area were calculated using the formula for area of an ellipse. On the tibial side, tunnel aperture area was calculated with respect to drill diameter and drill guide angle. Percentage of reconstructed area was calculated by dividing total tunnel aperture area by the native insertion site area.

RESULTS

The mean areas for the native femoral and tibial insertion sites were 83 ± 20 and 125 ± 20 mm(2), respectively. The mean tunnel aperture area for the femoral side was 65 ± 17, and 86 ± 17 mm(2) for the tibial tunnel aperture area. On average, percentage of reconstructed area was 79 ± 13 % for the femoral side, and 70 ± 12 % for the tibial side.

CONCLUSION

Anatomic ACL-R does not restore the native insertion site in its entirety. Percentage of reconstructed area serves as a rudimentary tool for evaluating the degree of native insertion site coverage using current individualized anatomic techniques and provides a starting point from which to evaluate the clinical significance of complete footprint restoration.

LEVEL OF EVIDENCE

IV.

Anatomic and morphological evaluation of the quadriceps tendon using 3-dimensional magnetic resonance imaging reconstruction: applications for anterior cruciate ligament autograft choice and procurement

BACKGROUND

The autograft of choice for anterior cruciate ligament (ACL) reconstruction remains controversial. The quadriceps tendon is the least utilized and least studied of the potential autograft options.

PURPOSE

To determine if the quadriceps tendon has the anatomic characteristics to produce a graft whose length and volume are adequate, reproducible, and predictable when compared with the other commonly used autografts.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Axial proton density magnetic resonance imaging (MRI) scans of 60 skeletally mature patients (30 male and 30 female) were evaluated. Volumetric analysis of 3-dimensional models of the patellar and quadriceps tendons was performed before and after the removal of a 10 mm-wide graft from both tendons. Length, thickness, and width measurements of the quadriceps tendon were made at predetermined locations. Anthropometric data were collected, and subgroup analysis, sex analysis, and linear regression were performed.

RESULTS

The mean percentage of volume remaining after removal of a 10 mm-wide graft from the patellar tendon was 56.6%, compared with 61.3% when harvesting an 80 mm-long graft of the same width from the quadriceps tendon. The intra-articular volume of the proposed quadriceps tendon graft was 87.5% greater than that of the patellar tendon graft. The mean length of the quadriceps tendon was 73.5 ± 12.3 mm in female patients and 81.1 ± 10.6 mm in male patients. These measurements were most highly correlated with patient height. The width of the quadriceps tendon decreased as one proceeded proximally from its insertion, and the thickness of the quadriceps tendon remained relatively constant.

CONCLUSION

The quadriceps tendon has the anatomic characteristics to produce a graft whose length and volume are both reproducible and predictable, while yielding a graft with a significantly greater intra-articular volume than a patellar tendon graft with a similar width.

Measurement of normal patellar ligament and anterior cruciate ligament by MRI and data analysis

The aim of this study was to obtain geometric data of in vivo patellar ligament (PL) and anterior cruciate ligament (ACL) by MRI and to analyze the correlation of the two with body weight, height and gender. A total of 157 cases with normal sagittal images of bilateral PL and ACL were enrolled. The PL and ACL lengths in the images were measured using the Radworks 5.1 application. The intraclass correlation coefficient for the data measured independently by three doctors was 0.997–1.000. In individuals aged 15–24 years, the values of PL and ACL length and the PL to ACL ratio were 43.95±4.25 mm, 38.45±4.62 mm and 1.15±1.09 in males and 42.03±0.94 mm, 36.00±1.06 mm and 1.18±0.1 in females, respectively. In individuals aged 25–64 years, the values in males were 40.99±4.45 mm, 36.06±3.74 mm and 1.14±0.09 and in females were 39.84±0.64 mm, 36.50±0.81 mm and 1.11±0.02, respectively. In individuals aged ≥65 years, the values in males were 41.43±3.08 mm, 36.62±3.44 mm and 1.15±0.09 and in females were 38.94±0.79 mm, 34.36±0.85 mm and 1.13±0.07, respectively. There was a significant difference between PL and ACL length on the same side (P<0.01). The data obtained was stable and repeatable. The present study established a database of PL and ACL length and the ratio of the two measured by MRI.

Avoiding mismatch in allograft anterior cruciate ligament reconstruction: correlation between patient height and patellar tendon length

PURPOSE

The purpose of this study was to evaluate whether a correlation exists between patient height and soft-tissue patellar tendon length.

METHODS

Magnetic resonance imaging (1.5 T) was performed for knee pathology on 403 patients. The patellar tendon length was measured in the midsagittal plane by a board-certified musculoskeletal radiologist. Patient height was recorded to the nearest inch. Patients were grouped into 6 subgroups with 4-inch range intervals based on height. The entire study group was analyzed. Subgroup analysis and gender analysis were performed to determine statistical significance.

RESULTS

The mean patellar tendon length was 45 +/- 7 mm (range, 30 to 66 mm). Wide ranges were noted among each height subgroup irrespective of gender. Significant differences were noted between most height subgroups independent of gender.

CONCLUSIONS

This study showed that a correlation exists between patient height, gender, and patellar tendon length. Although variation occurs among patients of the same height, significant differences in mean patellar tendon lengths do exist between patients in different height subgroups.

CLINICAL RELEVANCE

Parameters are provided using patient gender and height to reduce the potential for graft-construct mismatch when ordering bone-patellar tendon-bone allografts for anterior cruciate ligament reconstruction.

Preoperative magnetic resonance assessment of patellar tendon dimensions for graft selection in anterior cruciate ligament reconstruction

BACKGROUND

A bone patellar tendon bone autograft is one of the standard graft choices for anterior cruciate ligament reconstruction. However, its use can be limited when the patellar tendon is too narrow or too long.

HYPOTHESIS

A preoperative assessment of patellar tendon dimensions using magnetic resonance imaging would be accurate and reliable. Patients undergoing anterior cruciate ligament reconstruction would have wide ranges of patellar tendon dimensions, and a significant proportion of patients would have a too narrow and/or too long patellar tendon as the graft choice. There would be a demographic predictor to identify the patients with inappropriate patellar tendon dimensions.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

The accuracy and reliability of magnetic resonance assessments of patellar tendon dimensions were assessed by comparing the intraoperative measurements using a ruler in 55 knees and 10 knees, respectively. Data from the magnetic resonance assessments in 147 knees undergoing anterior cruciate ligament reconstruction were used for the normative documentation of the patellar tendon dimensions (width, thickness, and length) and identification of demographic predictors for the dimensions.

RESULTS

Preoperative magnetic resonance assessments of the patellar tendon dimensions were accurate and reliable. Korean patients undergoing anterior cruciate ligament reconstruction had wide variations in patellar dimensions, and a significant portion of the patients had an inappropriate patellar tendon (longer than 5 cm in 4.1% and narrower than 27 mm at middle portion in 15.6%) for the graft source. Patient height was the predictor used for patellar tendon width. The mathematical equation used to estimate the width based on patient height was: tendon width at middle portion (mm) = 0.202 x patient height (cm) - 5.07.

CONCLUSION

Preoperative magnetic resonance assessment of patellar tendon dimensions can be a valuable tool with satisfactory accuracy and reliability when the autologous patellar tendon is considered as the graft source for anterior cruciate ligament reconstruction.

Anthropometry of the patellar tendon in Chinese

PURPOSE

To assess the length of the patellar tendon in Chinese and its correlation with patient age, gender, and operated side.

METHODS

109 men and 11 women aged 15 to 45 (mean, 25) years underwent arthroscopic bone-tendon-bone reconstruction for anterior cruciate ligament (ACL) insufficiency. 55 (46%) injured the left side, and 65 (54%) the right side. Each patient's age, gender, and operated side were recorded. The length of the patellar tendon harvested was measured.

RESULTS

The mean length of the patellar tendon graft was 42.6 (standard deviation, 4.6; range, 30-54) mm. There was no correlation between the length of the patellar tendon and patient's age (p=0.147), gender (p=0.076), or operated side (p=0.466).

CONCLUSION

The length of the patellar tendon in the Chinese is comparable to that in Caucasians. Because of the shorter ACL but similar patellar tendon length, graft-tunnel mismatch may be more common in Chinese than Caucasian patients.

Peripheral versus aperture fixation for anterior cruciate ligament reconstruction

Because both the young and aging population are showing increasing interest in sports participation, the number of sports related injuries and in particular anterior cruciate ligament (ACL) injuries have been increasing. Because of these injuries much time and energy has been focused on ACL reconstruction in order to return these individuals to their optimal level of participation in their sport. This article explores and reviews the concepts of ACL fixation location and how this affects the ultimate outcome of this reconstructive procedure.

Bone-patella tendon-bone autograft anterior cruciate ligament reconstruction

The anterior cruciate ligament (ACL) serves an important stabilizing and biomechanical function for the knee. Reconstruction of the ACL remains one of the most commonly performed procedures in the field of sports medicine. Reconstruction of the ACL with bone-patella tendon-bone (BPTB) autograft secured with interference screw fixation has been the historical reference standard and remains the benchmark against which other methods are gauged. This article reviews the reconstruction of the ACL with BPTB autograft including the surgical technique, rationale for BTPB use, and outcomes.

The geometry of patella and patellar tendon measured on knee MRI

This study provides the geometry of patella and patellar tendon measured on sagittal and axial magnetic resonance images of 172 knees (142 males, 30 females) of 163 subjects (135 males, 28 females) whose mean age was 26.7. The gender difference and the relationship with anthropometry were also given. As for patella, the longitudinal lengths of the whole and articulating surface were 44.6, 32.9 mm, and the thickness was 22.3 mm. The mediolateral width was 45.8 mm, and the central ridge was located 19.9 mm or 43% lateral from the medial border. As for patellar tendon, the longitudinal length was 40.2 mm. The widths of proximal and distal part were 30.3, and 24.0 mm. The thicknesses of proximal and distal part were 3.2, and 5.0 mm. The geometry of the patella and patellar tendon was larger in male than in female (P < 0.001). Anthropometry including weight, height, body mass index corresponds well with the thickness of patella but poorly with the length of patellar tendon. These data can provide useful information in the field of knee surgery and sports medicine.

Avoiding allograft length mismatch during anterior cruciate ligament reconstruction: patient height as an indicator of appropriate graft length

BACKGROUND

Given the increasing use of allografts in anterior cruciate ligament reconstruction, selection of appropriate-sized grafts may help individual surgeons as well as the efficiency of the overall system for graft distribution.

HYPOTHESIS

Recipient patient height can predict the desired length for the tendinous portion of a patellar bone-tendon-bone allograft in anterior cruciate ligament reconstruction.

STUDY DESIGN

Cohort study (Prognosis); Level of evidence, 2.

METHODS

A series of 414 knees in 392 consecutive patients undergoing magnetic resonance imaging evaluation of knee pain were enrolled in the study. Data collected from magnetic resonance imaging included patella and patellar tendon length and intraarticular length of the anterior cruciate ligament. Patient age, height, weight, and gender were recorded. Linear regression analysis assessed the correlation between patient height and intraarticular length of the anterior cruciate ligament as well as patellar tendon length. The effect of variance in age, weight, and gender on anterior cruciate ligament intraarticular length was also measured.

RESULTS

A strong positive correlation was found between intraarticular length of the anterior cruciate ligament and patient height (Pearson r = 0.73; P < .001). Anterior cruciate ligament length (y, in millimeters) as a function of height (x, in inches) can be expressed as y = 1.17x - 41.29. As a function of height (x, in centimeters), anterior cruciate ligament length (y, in millimeters) can be expressed as y = 0.4606x - 41.29. Age, gender, and weight did not significantly influence this relationship. A weak positive association was found between patient height and patellar tendon length.

CONCLUSION

Patient height can predict the desired length of the tendinous portion of a patellar bone-tendon-bone allograft. An addition of 10 mm is made to the predicted anterior cruciate ligament length to allow for aperture tibial and femoral fixation. Patellar bone-tendon-bone allografts can be requested based on recipient patient height as follows: 5 ft, 0 in to 5 ft, 6 in: tendinous length/total length, 45 mm/95 mm; 5 ft, 7 in to 6 ft, 1 in: 50 mm/100 mm; > 6 ft, 1 in: 55 mm/105 mm.

The effect of cyclic loading on rotated bone-tendon-bone anterior cruciate ligament graft constructs

BACKGROUND

Single-incision anterior cruciate ligament reconstruction with a bone-patellar tendon-bone construct is commonly performed with 180 degrees rotation of the graft. It has been hypothesized that further rotation of the graft to 540 degrees can effectively shorten the graft to address graft length-tunnel mismatch. Initial biomechanical failure characteristics of rotated constructs have been reported, but cyclic loading of tendons has not been performed.

HYPOTHESIS

Graft rotation affects the biomechanical properties of the construct.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-five bone-patellar tendon-bone composite porcine right knee specimens were randomized into 3 groups and were externally rotated to 0 degrees , 180 degrees , or 540 degrees . Each group was then cyclically loaded in an artificial synovial fluid medium between 50 and 250 N for 5,000 cycles, loaded between 50 and 500 N for an additional 5,000 cycles, and finally subjected to load-to-failure testing.

RESULTS

Graft rotation shortened constructs by 1.7 +/- 0.8 mm at 180 degrees of rotation and 7.6 +/- 2.0 mm at 540 degrees of rotation (P < .01). There was a statistically significant increase in strain during cyclic loading at 540 degrees . No significant differences in maximum load, yield stress, yield strain, or modulus of elasticity were detected in single-cycle load-to-failure testing after cyclic loading.

CONCLUSION

Rotation of bone-patellar tendon-bone constructs to 540 degrees predictably shortens the effective graft length at the expense of increased strain with cyclic loading at stresses equivalent to walking and running.

CLINICAL RELEVANCE

Although rotation to 540 degrees potentially addresses graft length-tunnel mismatch, further clinical evaluation is required to evaluate the impact of increased strain on knee laxity and to determine the effects of physiologic loading of rotated bone-patellar tendon-bone constructs in vivo.

Effects of graft rotation on initial biomechanical failure characteristics of bone-patellar tendon-bone constructs

BACKGROUND

Graft-tunnel mismatch is a potential problem during single-incision technique for anterior cruciate ligament reconstruction with the central third of the patellar tendon. Mismatch is present when the graft is too long to fit appropriately in the tunnels that have been created. Graft rotation is one method for addressing this problem.

PURPOSE

To determine the results of graft rotation up to 540 degrees on initial graft biomechanical properties and graft length.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty porcine bone-patellar tendon-bone constructs were divided into four groups and constructs were rotated to 0 degrees, 90 degrees, 180 degrees, and 540 degrees, respectively, for each group. Biomechanical testing to failure was performed with the constructs under tension at an elongation rate of 5 cm/sec. Lengths were measured after a 1-kg load was applied to the grafts.

RESULTS

No statistical difference in ultimate failure strength was encountered between any of the groups (P = 0.915). The grafts that were twisted to 540 degrees shortened an average of 5.41 mm, which represented an average shortening of 10% of the initial tendon length.

CLINICAL RELEVANCE

Graft rotation up to 540 degrees does not result in loss of initial graft strength, and may be a solution for graft-tunnel mismatch.

The effect of outlet fixation on tunnel widening

PURPOSE

To compare the development of tibial tunnel widening after a standard bone-patellar tendon-bone autograft (BPTB) to a flipped BPTB that allows interference screw outlet fixation with a bone plug at both femoral and tibial tunnels, and to identify any observable clinical effect. The hypothesis of this study was that the outlet fixation achieved by the flipped BPTB technique results in diminished tunnel widening at the site of the bone plug. Type

TYPE OF STUDY

Nonrandomized control trial.

METHODS

The postoperative radiographs of 67 BPTB anterior cruciate ligament (ACL) reconstructions were retrospectively reviewed; 31 had conventional BPTBs and 36 had the bone plugs flipped at the tibial end to achieve interference screw fixation of the bone plug at the tibial outlet as well as the femoral outlet. Biodegradable interference screws (PLLA) were used in all cases, which facilitated tunnel measurements. One week after surgery, the maximal tibial bone tunnel widths were measured on anteroposterior and lateral radiographs 1 cm below the tibial plateau. These initial postoperative measurements were compared with measurement from radiographs taken annually thereafter. Clinical information including Lysholm, Tegner, IKDC activity, Lachman, pivot-shift, and range of motion data was also obtained and compared for the 2 groups.

RESULTS

In the conventional BPTB group, at an average follow-up of 28 months, 28 of 31 (90%) showed at least a 2-mm increase (20%) in the tibial tunnel width. The mean maximum tunnel width increase was 2.2 mm. In the flipped BPTB group, at an average follow-up of 31 months, none of these 36 showed any increase in tunnel size. In fact, 15 patients had no distinct tibial tunnel remaining and, of the other 21, the average remaining tunnel width was 3 mm. The clinical results evaluating the Tegner, Lysholm, IKDC activity levels, KT, and physical examination parameters showed no significant differences between these 2 groups. The tunnel width decreased during the first year, but remained unchanged after 12 months. No tunnel dilation was observed with bone plug outlet fixation while 90% of the conventional group had at least a 20% increase (P <.001).

CONCLUSIONS

Outlet fixation with the flipped BPTB technique decreased the tibial tunnel width 1 cm below the plateau while 90% of the conventional BPTB patients demonstrated an average widening of 20%.

Endoscopic anterior cruciate ligament reconstruction with patella tendon autograft

The patella tendon is the most commonly used graft source for ACL reconstruction because of its biomechanical strength and stiffness, the availability of bone-to-bone healing on either end, and the ability to firmly secure the graft within the tunnels. Consistently good results have been reported in the literature, with expectations to return to all activities at pre-injury levels of performance. We outline our technique for endoscopic ACL reconstruction using a patella tendon autograft. The technique is divided into the critical stages of pre-operative assessment, graft harvest, notch preparation, tunnel placement, graft passage, graft fixation, and rehabilitation. Methods for avoiding pitfalls and overcoming mishaps are described.

A bioabsorbable plug in bone-tendon-bone reconstruction of the anterior cruciate ligament: Introduction of a novel fixation technique

PURPOSE

Our aim was to compare the fixation strength of a novel plugging technique with that of the conventional interference technique in bone-patellar tendon-bone reconstruction of the anterior cruciate ligament.

TYPE OF STUDY

Randomized experimental study.

METHODS

Twenty matched pairs of porcine knees were randomly assigned to 2 groups. The bone block of the graft was secured in the femoral drill hole with either the new bioabsorbable poly-L-lactide/D-lactide (PLA 96/4) copolymer plug (plugging technique) (n = 20) or a conventional interference screw (interference technique) (n = 20). Ten pairs were subjected to a single cycle loading test at a rate of 50 mm/min while the remaining 10 pairs underwent a cyclic loading test to further assess the quality of the fixation. The cyclic loading test consisted of 1,500 loading cycles between 50 and 200 N at half-hertz frequency, after which the specimens were loaded to failure at a rate of 50 mm/min.

RESULTS

In the single cycle loading test, the average ultimate failure load was 1,061 +/- 342 N in the plugging technique group and 971 +/- 260 N in the interference technique group (P =.57). Significant group differences were found neither in the yield loads nor in the stiffness of the fixations. In the cyclic loading, significant displacement difference was not observed between the 2 fixation techniques. There were neither significant group differences with regard to the ultimate failure load (plugging technique 994 +/- 376 N versus interference technique 1,001 +/- 343 N, P =.97) nor yield load of the fixations in the subsequent single cycle loading.

CONCLUSIONS

The results of this study indicate that, in anterior cruciate ligament reconstruction, the new plugging technique is a reasonable alternative for fixation of the femoral site of a bone-patellar tendon-bone graft.