Eighteen-year outcome of anterior cruciate ligament reconstruction with patellar tendon or hamstring autograft.

PURPOSE: To evaluate patient reported outcomes and radiographic arthritic changes of transtibial anterior cruciate ligament reconstruction (ACLR) with either bone-patellar tendon-bone (BPTB) or hamstrings (HS) auto-grafts at a minimum of 15-year follow-up. METHODS: Ninety-four patients (51 of the HS group, 43 of BPTB group) who were operated between the years 2000 to 2005 in two tertiary referral hospitals were contacted and invited to a retrospective evaluation. The interview included subjective outcomes using the Lysholm knee scoring questionnaire, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Tegner activity level scale, Visual Analogue Scale (VAS) for pain and patients' satisfaction scale. Knee examination included measurements of motion and stability. Knee radiographs were evaluated for osteoarthritic changes according to the Kellgren-Lawrence (KL) score. RESULTS: The average evaluation time from surgery was 18.6 years. Subjectively, there was no significant difference between groups except for a better post-operative level of activity and satisfaction in the HS group. Objectively, there was no significant difference between groups in knee stability and range of motion. Most patients had grade KL ≤ 1 radiographic osteoarthritits changes and there was no significant difference between groups. Recurrent complete tear of the reconstructed graft occurred in 3 patients of each group. In both groups 84% had no further surgery while the indications for further surgery were mostly a meniscal tear or tibial hardware removal. CONCLUSIONS: Very long-term outcomes and clinical stability of transtibial HS or BPTB graft ACL reconstruction are good with low rate of graft failure and radiographic osteoarthritis.

Surgical treatment of patellar tendon rupture after total knee arthroplasty with a double-row repair method using the hamstring tendons: A novel technique with functional results.

BACKGROUND: Patellar tendon rupture (PTR) is extremely rare but serious complication after primary or revision total knee arthroplasty. Due to the serious failure rates of end-to-end repair techniques, various augmentation techniques have been described. In this study, the results of patients with PTR after reconstruction using our own technique with semitendinosus (ST) and gracilis tendons taken from the affected side were evaluated retrospectively. METHODS: A total of 14 patients, whose diagnosis was made based on physical examination and clinical findings, and supported radiologically (ultrasonography), were included in the study. In these patients, reconstruction was performed using double-row repair technique with the ST and gracilis tendons. Active-passive knee joint range of motion, active knee extension loss, and the Caton-Deschamps index at preoperative and final follow-up visits were compared. Tegner-Lysholm knee score and Kujala score were used to evaluate functional results. RESULTS: In 14 patients (8 women and 6 men) with a mean age of 68.1 years, the median time between injury and surgery was 6.6 weeks. In all patients, the rupture was in the distal part of the patellar tendon. While the median preoperative Caton-Deschamps index was 1.8, the postoperative median value was found to be 1.25 after an average follow-up of 3.8 years (P = .014). The median preoperative knee extension loss decreased from 25° to 5° postoperatively. Tegner-Lysholm knee score and Kujala score of the patients at their last follow-up were significantly increased (P < .01). CONCLUSION: For PTR developing after total knee arthroplasty, the double-row reconstruction technique with ST and gracilis tendons is effective.

Strength and Functional Outcomes Following Achilles Tendon Reconstruction With Hamstring Tendon Autograft Augmentation.

BACKGROUND: The proposed advantages of hamstring autograft reconstruction when compared to alternative procedures, such as flexor hallucis longus (FHL) transfer, V-Y lengthening, and allograft reconstruction, are improved healing and reproduction of normal tendon biomechanics and reduced morbidity within the foot and ankle. In this study, we examined the effect of Achilles tendon reconstruction using hamstring autografts on strength and functional outcomes. METHODS: Patients who underwent Achilles repair with a hamstring autograft for insertional or midsubstance tendinopathy, delayed diagnosis of rupture, or infection after primary repair were evaluated for inclusion. Forty-six patients were identified; 12 further augmented with an FHL transfer are included in the analysis. Isokinetic testing was completed with a Biodex dynamometer under supervision of a physical therapist masked to surgical side. Pre- and postoperative Foot and Ankle Outcome Scores (FAOS, before March 2016) or Patient-Reported Outcomes Measurement Information System (PROMIS, after March 2016) surveys were collected. RESULTS: For knee flexion, peak torque was not significantly different when comparing operative and nonoperative sides at 180 degrees/second (45.38 Nm vs 45.96 Nm; P = .69) nor at 300 degrees/second (44.2 Nm vs 47.02 Nm; P = .069). Knee extension absolute peak torque was only found to be significantly weaker on the operative side at the faster testing (75.5 Nm vs 79.56 Nm; P < .05). Peak ankle plantarflexion torque was significantly weaker on the operative side at both the slower speed (60 degrees/second: 39.9 Nm vs 48.76 Nm; P < .005) and the faster speed (120 degrees/second: 31.3 Nm vs 40.7 Nm; P < .001). Average power for ankle plantarflexion did not differ significantly from the operative side to the nonoperative side in the slower test (26.46 W vs 27.48 W; P = .60) but did significantly differ on the faster test (32.13 W vs 37.63 W; P = .041). At an average of 19.9 months postoperation, all physical function and pain-related patient-reported outcome scores showed clinically and statistically significant improvement. CONCLUSION: Achilles reconstruction with a hamstring autograft ± FHL transfer allowed patients with severe Achilles pathology to return to good subjective function, with modest deficits in calf strength compared with the uninjured side. Overall knee flexion strength did not appear impaired. These results suggest that hamstring autograft reconstruction is a viable method to treat these complex cases involving a lack of healthy tissue, allowing patients to return to symptom-free physical function and athletic activity. LEVEL OF EVIDENCE: Level IV, case series.

Hamstring Tendon Autograft Is Associated With Increased Knee Valgus Moment After Anterior Cruciate Ligament Reconstruction: A Biomechanical Analysis.

BACKGROUND: There is limited evidence related to the effects of autograft type on functional performance after anterior cruciate ligament reconstruction (ACLR). PURPOSE/HYPOTHESIS: This study aimed to compare biomechanical outcomes during a drop vertical jump (DVJ) between patients with a hamstring tendon (HT) autograft, quadriceps tendon (QT) autograft with bone block, QT autograft without bone block, and bone-patellar tendon-bone autograft at 6 months postoperatively in an adolescent population. The authors' hypothesized there would be differences in DVJ biomechanics between athletes depending on the type of autograft used. STUDY DESIGN: Controlled laboratory study. METHODS: Patients aged 8 to 18 years who underwent primary ACLR were included for analysis. Kinematic and kinetic data collected during a DVJ using a 3-dimensional computerized marker system were assessed at 6 months after ACLR and compared with the uninjured contralateral limb. RESULTS: A total of 155 participants were included. There were no significant differences in terms of age, sex, or affected leg (P≥ .1973) between groups. The HT group was significantly associated with a larger knee valgus moment at initial contact compared with the QT group (28 × 10-2 vs -35 × 10-2 N·m/kg, respectively; P = .0254) and a significantly larger maximum hip adduction moment compared with the QT with bone block group (30 × 10-2 vs -4 × 10-2 N·m/kg, respectively; P = .0426). Both the QT with bone block (-12 × 10-2 vs -3 × 10-2 N·m/kg, respectively; P = .0265) and QT (-13 × 10-2 vs -3 × 10-2 N·m/kg, respectively; P = .0459) groups demonstrated significantly decreased mean knee extension moments compared with the HT group. CONCLUSION: The findings of this study suggest that utilizing an HT autograft resulted in a significantly increased knee valgus moment at initial contact compared with a QT autograft without bone block at 6 months after ACLR in adolescent patients performing a DVJ. A QT autograft was found to be associated with significantly decreased extensor mechanism function compared with an HT autograft. CLINICAL RELEVANCE: This study adds unique kinematic and kinetic information regarding various ACLR autograft options and highlights the biomechanical deficits that should be taken into consideration in rehabilitation.

No Difference in Bone Tunnel Enlargement and Clinical Outcome between Cortical Suspension and Hybrid Femoral Fixation in Hamstring Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: The best method for femoral fixation in anterior cruciate ligament reconstruction (ACLR) remains controversial. The study assesses the bone tunnel enlargement and clinical outcome in hamstring ACLR using cortical suspension or hybrid (cortical suspension and compression) femoral fixation. METHODS: From January 2010 to December 2021, 102 patients who underwent quadruple hamstring ACLR using cortical suspension (39 patients) or hybrid (63 patients) fixation on the femoral side were retrospectively analyzed. Clinical evaluation was conducted using the international knee documentation committee score, the Lysholm score, the Tegner activity level scale, the knee injury and osteoarthritis outcome score (quality of life score), the Lachman test, and the side-to-side difference by the KT-1000 arthrometer. The complications after the surgery were also evaluated. These data were compared at baseline and last follow-up. The diameters of the femoral tunnel were calculated at three sites: the width of the entrance of the femoral tunnel, 1 cm proximal to the entrance of the femoral tunnel and the largest diameter of the femoral tunnel on magnetic resonance imaging (MRI) coronal images. Bone tunnel widening data were contrasted between MRI images conducted at least 2 years and within 2 weeks after surgery. The morphology of bone tunnel enlargement was also observed and recorded. The categorical parameters were analyzed using the χ2-test and Fisher's exact test. The continuous variables conforming to a normal distribution were analyzed using Student's t-test, and the Mann-Whitney U-test was undertaken between the two groups without normal distribution. RESULTS: Both cortical suspension and hybrid femoral fixation in quadruple hamstring ACLR achieved significantly improved patient-reported outcome scores and knee stability compared to preoperative data. However, no significant differences were found between these two methods in clinical evaluations, postoperative complications, and patient-reported outcome scores. Although the mean diameter of the enlarged bone tunnel was lowered by an additional bioabsorbable interference screw fixation near the joint line, a statistically insignificant difference was found between the hybrid and cortical suspension fixation on the femoral side. There was no statistical difference in the distribution of enlarged bone tunnel morphology between groups. CONCLUSIONS: No significant difference was found in the bone tunnel enlargement and clinical outcome between cortical suspension and hybrid femoral fixation in ACLR using hamstring autograft.

Comparison of the Clinical Outcomes between All-inside and Standard Technique in Anterior Cruciate Ligament Reconstruction with 6-strand Hamstring Tendon Autograft.

OBJECTIVE: All-inside and standard techniques with 4-strand hamstrings graft have been widely used in anterior cruciate ligament (ACL) reconstruction. However, the graft diameter of less than 8 mm will significantly increase the rate of surgical failure, and the 6-strand graft can solve this problem. The purpose of this study is to compare all-inside ACL reconstruction using suspensory cortical button fixation on both tibia and femur with standard ACL reconstruction using suspensory femoral fixation and a bioabsorbable tibial interference screw with a 6-strand hamstring tendon autograft in postoperative clinical outcomes. METHODS: From January 2020 to December 2020, 48 patients performed ACL reconstruction were divided into the all-side group and the standard group according to the different surgical techniques. Magnetic resonance imaging (MRI) and subjective function scores was used to assess clinical outcomes at least 24 months following ACL reconstruction. MRI was used to measure the value of bone tunnel widening in articular and middle portions. Subjective function scores included the Lysholm knee score, the International Knee Documentation Committee (IKDC) score, the Knee Society Score (KSS) for pain and function, and KT-1000. The t-test was used assuming the distribution of the patients which follows the normal distribution and we used non-parametric tests if these two conditions were not satisfied. RESULTS: At the final follow-up, there were 22 patients in the all-inside group and 24 patients in the standard group. No significant differences were found with respect to femoral tunnel widening and subjective function scores. However, a significant increase in tibial tunnel widening was found in the middle portion of the standard group (2.25 ± 0.74) compared to the all-inside group (0.76 ± 0.24) (p < 0.01) and also in the articular portion of the standard group (2.07 ± 0.77) compared to the all-inside group (1.52 ± 0.54) (p = 0.02). In addition, the value of the KT-1000 was 1.81 ± 0.45 for the all-inside group and 2.12 ± 0.44 in the standard group (p = 0.016). CONCLUSION: The objective stability of the knee was relatively better in the all-inside group than in the standard group. And tunnel widening after ACL reconstruction was significantly greater in the standard technique when compared to the all-inside technique on the tibia side.

The NordBord test reveals persistent knee flexor strength asymmetry when assessed two and five years after ACL reconstruction with hamstring tendon autograft.

OBJECTIVE: Comparison of knee flexor strength limb symmetry index (LSI) between the NordBord-test and the Biodex-test, and to determine the relationship between knee flexor strength and function in patients 2 and 5 years after anterior cruciate ligament reconstruction (ACL-R) with hamstring tendon (HT) autografts. DESIGN: Observational registry study. SETTING: Primary care. PATIENTS: Cross-sectional data from 96 patients (55% women) participating in a rehabilitation-registry after ACL-R with HT autografts. MAIN OUTCOME MEASURES: Comparison of knee flexor strength symmetry between the Biodex-test and the NordBord-test. Secondly, the relationship between knee flexor strength test and perceived knee function, activity level, and hop performance. RESULTS: The NordBord-test demonstrated greater strength deficits compared to the Biodex-test with a mean difference of 12.5% ± 15.1% 95 % CI [8.1; 16.9%] at 2 years, and 11.1% ± 11.9% 95 % CI [7.7; 14.6 %] at 5 years after ACL-R. Relative concentric knee flexor strength (Nm/kg) in the Biodex demonstrated significant weak-to-moderate correlations with activity level and hop performance (r = 0.33-0.67) at 2 and 5 years. CONCLUSION: The NordBord-test identified deficits in knee flexor strength LSI not seen with the Biodex-test at 2 and 5 years after ACL-R. No significant correlations were found between the persistent knee flexor strength asymmetry and perceived function, activity level or hop performance.

Anterior Cruciate Ligament Reconstruction with Semitendinosus Tendon Autograft among Paramilitary Patients Undergoing Arthroscopic Surgery in a Tertiary Care Centre.

Introduction: In orthopaedic practice, injuries to the anterior cruciate ligaments occur almost on an epidemic scale, yet it continues to be of interest in orthopaedic surgery whether semitendinosus or gracilis hamstring autografts can be used for better anterior cruciate ligament reconstruction. This study aimed to determine the prevalence of anterior cruciate ligament reconstruction using semitendinosus tendon autografts among paramilitary patients undergoing arthroscopic surgery in a tertiary care centre. Methods: This descriptive cross-sectional study was conducted among paramilitary individuals who had knee injuries and were admitted between 6 february 2020 and 26 January 2022 for arthroscopic surgery after obtaining ethical approval from the Institutional Review Committee. Demographic details and the mode of injury were obtained from the patients. The treating orthopaedic surgeons evaluated the pre- and post-analysis Lysholm Knee Score and Lysholm Knee Scale based on the patient's response. A convenience sampling method was used. The point estimate was calculated at a 95% Confidence Interval. Results: Among 166 patients, anterior cruciate ligament reconstruction using a semitendinosus tendon autograft was done in 58 (34.94%) (27.69-42.19, 95% Confidence Interval). Most of the patients in the pre-analysis had mild/periodic limp issues 52 (89.66%), followed by instability during athletics or other severe exertion 43 (74.14%). Conclusions: The prevalence of anterior cruciate ligament injuries in our study is higher than other studies done in similar settings. Keywords: anterior cruciate ligament; grafts; semitendinosus tendon.

Increased risk for early revision with quadriceps graft compared with patellar tendon graft in primary ACL reconstructions.

PURPOSE: Bone patella-tendon bone (BPTB) and hamstring tendon (HT) autografts are the most used grafts in primary anterior cruciate ligament (ACL) reconstructions (ACLR) in Norway. Quadriceps tendon (QT) autograft has gained more popularity during the past years. The purpose of this study is to compare revision rates and patient-reported outcomes of primary QT with BPTB and HT autograft ACL reconstructions in Norway at 2-year follow-up. It was hypothesized that there would be no difference in 2-year revision rates between all three autografts. METHODS: Data included primary ACLR without concomitant ligament surgeries, registered in the Norwegian Knee Ligament Register from 2004 through 2021. Revision rates at 2 years were calculated using Kaplan-Meier analysis. Hazard ratios (HR) for revision were estimated using multivariable Cox regression analysis with revision within 2 years as endpoint. Mean change in patient-reported outcome was recorded preoperatively and at 2 years through the Knee Injury and Osteoarthritis Outcome Score (KOOS) subcategories 'Sport' and 'Quality of Life' was measured for patients that were not revised and analysed with multiple linear regression. RESULTS: A total of 24,790 primary ACLRs were identified, 10,924 with BPTB, 13,263 with HT and 603 with a QT graft. Patients in the QT group were younger (23.5 years), more of them were women (58.2%) and over 50% had surgery <3 months after injury. The QT group had the highest prevalence of meniscal injuries (61.9%). Revision estimates at 2-years were 3.6%, 2.5% and 1.2% for QT, HT and BPTB, respectively (p < 0.001). In a Cox regression analysis with QT as reference, BPTB had a lower risk of revision (HR 0.4, 95% Cl 0.2-0.7, p < 0.001). No significant difference was observed in the revision risk between QT and HT (HR 1.1, 95% Cl 0.7-1.8, n.s.). The two most common reported reasons for revision were: traumatic graft rupture and nontraumatic graft failure. There were no differences between the groups in change of KOOS in subcategories 'Sport' and 'Quality of Life' at 2-years follow-up. CONCLUSION: The 2-year risk of revision after ACLR with QT was higher than BPTB and similar to HT. No difference was found between the groups in patient-reported outcomes. This study provides valuable insights for both surgeons and patients when making decisions about the choice of autografts in primary ACL reconstructions. LEVEL OF EVIDENCE: Level II.

Unsupervised Machine Learning of the Combined Danish and Norwegian Knee Ligament Registers: Identification of 5 Distinct Patient Groups With Differing ACL Revision Rates.

BACKGROUND: Most clinical machine learning applications use a supervised learning approach using labeled variables. In contrast, unsupervised learning enables pattern detection without a prespecified outcome. PURPOSE/HYPOTHESIS: The purpose of this study was to apply unsupervised learning to the combined Danish and Norwegian knee ligament register (KLR) with the goal of detecting distinct subgroups. It was hypothesized that resulting groups would have differing rates of subsequent anterior cruciate ligament reconstruction (ACLR) revision. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: K-prototypes clustering was performed on the complete case KLR data. After performing the unsupervised learning analysis, the authors defined clinically relevant characteristics of each cluster using variable summaries, surgeons' domain knowledge, and Shapley Additive exPlanations analysis. RESULTS: Five clusters were identified. Cluster 1 (revision rate, 9.9%) patients were young (mean age, 22 years; SD, 6 years), received hamstring tendon (HT) autograft (91%), and had lower baseline Knee injury and Osteoarthritis Outcome Score (KOOS) Sport and Recreation (Sports) scores (mean, 25.0; SD, 15.6). Cluster 2 (revision rate, 6.9%) patients received HT autograft (89%) and had higher baseline KOOS Sports scores (mean, 67.2; SD, 16.5). Cluster 3 (revision rate, 4.7%) patients received bone-patellar tendon-bone (BPTB) or quadriceps tendon (QT) autograft (94%) and had higher baseline KOOS Sports scores (mean, 65.8; SD, 16.4). Cluster 4 (revision rate, 4.1%) patients received BPTB or QT autograft (88%) and had low baseline KOOS Sports scores (mean, 20.5; SD, 14.0). Cluster 5 (revision rate, 3.1%) patients were older (mean age, 42 years; SD, 7 years), received HT autograft (89%), and had low baseline KOOS Sports scores (mean, 23.4; SD, 17.6). CONCLUSION: Unsupervised learning identified 5 distinct KLR patient subgroups and each grouping was associated with a unique ACLR revision rate. Patients can be approximately classified into 1 of the 5 clusters based on only 3 variables: age, graft choice (HT, BPTB, or QT autograft), and preoperative KOOS Sports subscale score. If externally validated, the resulting groupings may enable quick risk stratification for future patients undergoing ACLR in the clinical setting. Patients in cluster 1 are considered high risk (9.9%), cluster 2 patients medium risk (6.9%), and patients in clusters 3 to 5 low risk (3.1%-4.7%) for revision ACLR.

Difference of Knee Strength Recovery Between Revision and Primary ACL Reconstruction.

Different grafting procedures are available to restore knee stability after revision anterior cruciate ligament (ACL) reconstruction. We compared knee strength recovery between ACL revision surgery and primary reconstruction. One hundred and ten patients with ACL revision surgery were matched with 110 patients with primary reconstruction based on the graft procedure. The isokinetic knee strength had been assessed for the first 9 months post-surgery. Knee laxity, function, and activity score were also evaluated. Limb symmetry index for knee extensor and flexor strength was not different at 4-, 6- and 9-months post-surgery between revision surgery and primary reconstruction. These results depended on ipsilateral or contralateral graft choice. Ipsilateral hamstring tendon (HT) and contralateral bone-patellar-tendon-bone (BPTB) graft procedures were similar for a revision of a BPTB graft failure. Contralateral HT procedure was better than ipsilateral BPTB procedure for a revision of a HT graft failure. The early recovery of isokinetic knee strength after ACL revision surgery regardless of the HT or BPTB procedures, was similar to the recovery after primary ACL reconstruction with the same graft technique. These results apparently depended on a temporary quadriceps arthrogenic muscle inhibition and on a persistent donor site morbidity, concerning the new and the previous grafts, respectively.

A Prospective Randomized Controlled Trial Investigating Quadriceps Versus Hamstring Tendon Autograft in Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Numerous graft options are available when undertaking anterior cruciate ligament (ACL) reconstruction (ACLR), although a lack of high-quality evidence exists comparing quadriceps (QT) and hamstring (HT) autografts. PURPOSE: To investigate patient outcomes in patients undergoing HT versus QT ACLR. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: After recruitment and randomization, 112 patients (HT = 55; QT = 57) underwent ACLR. Patients were assessed pre- and postoperatively (6 weeks and 3, 6, 12, and 24 months), with a range of patient-reported outcome measures (PROMs), graft laxity (KT-1000 arthrometer; primary outcome variable), active knee flexion and extension range of motion (ROM), peak isokinetic knee extensor and flexor strength, and a 6-hop performance battery. Limb symmetry indices (LSIs) were calculated for strength and hop measures. Secondary procedures, ACL retears, and contralateral ACL tears were reported. RESULTS: All PROMs and knee ROM measures significantly improved (P < .0001), and no other group differences (P > .05) were observed-apart from the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) score, which was significantly better in the HT group at 3 (P = .008), 6 (P = .010), and 12 (P = .014) months. No significant changes were observed in side-to-side laxity from 6 to 24 months (P = .105), and no group differences were observed (P = .487) at 6 (HT mean, 1.2; QT mean, 1.3), 12 (HT mean, 1.1; QT mean, 1.3), and 24 (HT mean, 1.1; QT mean, 1.2) months. While the HT group demonstrated significantly greater (P < .05) quadriceps strength LSIs at 6 and 12 months, the QT group showed significantly greater (P < .05) hamstring strength LSIs at 6, 12, and 24 months. The HT group showed significantly greater (P < .05) LSIs for the single horizontal (6 months), lateral (6 and 12 months), and medial (6 months) hop tests for distance. Up until 24 months, 1 patient (QT at 22 months) had a retear, with 2 contralateral ACL tears (QT at 19 months; HT at 23 months). Secondary procedures included 5 in the HT group (manipulation under anesthesia, notch debridement, meniscal repair, and knee arthroscopy for scar tissue) and 6 in the QT group (notch debridement, meniscal repair, knee arthroscopy for scar tissue, tibial tubercle transfer, and osteochondral autologous transplantation). CONCLUSION: Apart from the ACL-RSI, the 2 autograft groups compared well for PROMs, knee ROM, and laxity. However, greater hamstring strength LSIs were observed for the QT cohort, with greater quadriceps strength (and hop test) LSIs in the HT cohort. The longer-term review will continue to evaluate return to sports and later-stage reinjury between the 2 graft constructs. REGISTRATION: ACTRN12618001520224p (Australian New Zealand Clinical Trials Registry).

External validation of the Norwegian anterior cruciate ligament reconstruction revision prediction model using patients from the STABILITY 1 Trial.

PURPOSE: A machine learning-based anterior cruciate ligament (ACL) revision prediction model has been developed using Norwegian Knee Ligament Register (NKLR) data, but lacks external validation outside Scandinavia. This study aimed to assess the external validity of the NKLR model (https://swastvedt.shinyapps.io/calculator_rev/) using the STABILITY 1 randomized clinical trial (RCT) data set. The hypothesis was that model performance would be similar. METHODS: The NKLR Cox Lasso model was selected for external validation owing to its superior performance in the original study. STABILITY 1 patients with all five predictors required by the Cox Lasso model were included. The STABILITY 1 RCT was a prospective study which randomized patients to receive either a hamstring tendon autograft (HT) alone or HT plus a lateral extra-articular tenodesis (LET). Since all patients in the STABILITY 1 trial received HT ± LET, three configurations were tested: 1: all patients coded as HT, 2: HT + LET group coded as bone-patellar tendon-bone (BPTB) autograft, 3: HT + LET group coded as unknown/other graft choice. Model performance was assessed via concordance and calibration. RESULTS: In total, 591/618 (95.6%) STABILITY 1 patients were eligible for inclusion, with 39 undergoing revisions within 2 years (6.6%). Model performance was best when patients receiving HT + LET were coded as BPTB. Concordance was similar to the original NKLR prediction model for 1- and 2-year revision prediction (STABILITY: 0.71; NKLR: 0.68-0.69). Concordance 95% confidence interval (CI) ranged from 0.63 to 0.79. The model was well calibrated for 1-year prediction while the 2-year prediction demonstrated evidence of miscalibration. CONCLUSION: When patients in STABILITY 1 who received HT + LET were coded as BPTB in the NKLR prediction model, concordance was similar to the index study. However, due to a wide 95% CI, the true performance of the prediction model with this Canadian and European cohort is unclear and a larger data set is required to definitively determine the external validity. Further, better calibration for 1-year predictions aligns with general prediction modelling challenges over longer periods. While not a large enough sample size to elicit the true accuracy and external validity of the prediction model when applied to North American patients, this analysis provides more support for the notion that HT plus LET performs similarly to BPTB reconstruction. In addition, despite the wide confidence interval, this study suggests optimism regarding the accuracy of the model when applied outside of Scandinavia. LEVEL OF EVIDENCE: Level 3, cohort study.

Metal interference screw fixation combinations show high revision rates in primary hamstring tendon ACL reconstruction.

BACKGROUND: Different fixation methods in anterior cruciate ligament reconstruction (ACLR) have been associated with different revision rates, specifically in the early postoperative period. However, most previous research has either grouped together different fixation types or evaluated femoral-sided fixation or tibial-sided fixation separately. Therefore, the purpose of this study was to determine ACL revision rates for specific combinations of femoral and tibial fixation methods within 2 years of primary hamstring tendon autograft ACLR based on data from the Swedish National Knee Ligament Registry (SNKLR). METHODS: Patients that underwent primary hamstring tendon autograft ACLR between 2005 and 2018 in the SNKLR were included. The collected data included patient characteristics (age, sex, body mass index [BMI]), activity at time of injury, surgical information (concomitant injuries, time from injury to surgery, fixation types at the femur and tibia), and subsequent revision ACLR. Revision rate within 2 years of the index procedure was chosen, as ACLR fixation is most likely to contribute to ACLR revision within the first 2 years, during graft maturation. RESULTS: Of the 23,238 included patients undergoing primary hamstring ACLR, 581 (2.5%) underwent revision ACLR within 2 years of the index procedure. Among the combinations used for > 300 patients, the femoral metal interference screw/tibial metal interference screw fixation combination had the highest revision rate followed by metal interference screw/resorbable screw and Endobutton/AO screw fixation combinations, with respective revision rates of 4.0, 3.0, and 3.0%. The lowest revision rate within 2 years of ACLR was found in the Endobutton/metal interference screw with backup Osteosuture fixation combination, used in 433 cases, with a failure rate of 0.9%. CONCLUSION: Different early ACL revision rates were found across different combinations of femoral and tibial fixation devices within 2 years of primary hamstring tendon autograft ACLR. Metal interference screw fixation, particularly when performed on both the femoral and tibial sides, most frequently resulted in revision ACLR. These findings may be helpful for surgeons in selecting appropriate fixation devices for hamstring ACLR. LEVEL OF EVIDENCE: IV.

Influence of Graft Type and Meniscal Involvement on Short-Term Outcomes Following Anterior Cruciate Ligament Reconstruction.

CONTEXT: The purpose of this study was to compare short-term clinical outcomes between meniscus procedures performed with anterior cruciate ligament reconstruction (ACLR), ACLR (ACLR-only), ACLR with meniscectomy/resection (ACLR-resect), and ACLR with meniscal repair (ACLR-repair) for bone patellar tendon bone grafts (BPTB) and hamstring tendon grafts, separately. DESIGN: This was a cross-sectional study conducted in a controlled laboratory setting as part of a large point-of-care collaborative research program. METHODS: This study included 314 participants (168 females; mean [SD]: age, 19.7 [4.8]) with primary unilateral ACLR with a BPTB or hamstring tendon. Patients were divided into 3 groups depending on meniscal procedure (ACLR-only, ACLR-resect, and ACLR-repair). Postsurgical testing included: isokinetic assessment of knee extension and flexion, single-leg hop tests, and patient-reported outcomes. Multivariate analysis of covariance compared differences between meniscal procedures on the battery of tests, and for each statistically significant variable an analysis of covariance assessed the effect of meniscal procedure within each graft type. Chi-square analysis assessed the influence of meniscal procedure on tests' pass rates defined as 90% of limb symmetry index. RESULTS: BPTB: ACLR-only had greater hamstring strength than ACLR-resect (P = .05) and ACLR-repair (P = .005). ACLR-only had the highest proportion of participants to pass the hamstring strength test (P = .02). Hamstring tendon: ACLR-only (P = .03) and ACLR-resect (P = .003) had higher International Knee Documentation Committee scale scores than ACLR-repair. There was a significant difference in the proportion of participants who scored >90% limb symmetry index on the timed hop test (P = .05). CONCLUSIONS: The influence of meniscal repair on clinical outcomes is dependent on the graft choice. Following an ACLR with BPTB and a meniscal procedure, hamstring function should be more closely monitored for optimal short-term recovery.

Weaker Quadriceps Muscle Strength With a Quadriceps Tendon Graft Compared With a Patellar or Hamstring Tendon Graft at 7 Months After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Impaired quadriceps muscle strength after anterior cruciate ligament reconstruction (ACLR) is associated with worse clinical outcomes and a risk of reinjuries. Yet, we know little about quadriceps muscle strength in patients reconstructed with a quadriceps tendon (QT) graft, which is increasing in popularity worldwide. PURPOSE: To describe and compare isokinetic quadriceps strength in patients undergoing ACLR with a QT, hamstring tendon (HT), or bone-patellar tendon-bone (BPTB) autograft. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We included patients with QT grafts (n = 104) and matched them to patients with HT (n = 104) and BPTB (n = 104) grafts based on age, sex, and associated meniscal surgery. Data were collected through clinical strength testing at a mean of 7 ± 1 months postoperatively. Isokinetic strength was measured at 90 deg/s, and quadriceps strength was expressed as the limb symmetry index (LSI) for peak torque, total work, torque at 30° of knee flexion, and time to peak torque. RESULTS: Patients with QT grafts had the most impaired isokinetic quadriceps strength, with the LSI ranging between 67.5% and 75.1%, followed by those with BPTB grafts (74.4%-81.5%) and HT grafts (84.0%-89.0%). Patients with QT grafts had a significantly lower LSI for all variables compared with patients with HT grafts (mean difference: peak torque: -17.4% [95% CI, -21.7 to -13.2], P < .001; total work: -15.9% [95% CI, -20.6 to -11.1], P < .001; torque at 30° of knee flexion: -8.8% [95% CI, -14.7 to -2.9], P = .001; time to peak torque: -17.7% [95% CI, -25.8 to -9.6], P < .001). Compared with patients with BPTB grafts, patients with QT grafts had a significantly lower LSI for all variables (mean difference: peak torque: -6.9% [95% CI, -11.2 to -2.7], P < .001; total work: -7.7% [95% CI, -12.4 to -2.9], P < .001; torque at 30° of knee flexion: -6.3% [95% CI, -12.2 to -0.5], P = .03; time to peak torque: -8.8% [95% CI, -16.9 to -0.7], P = .03). None of the graft groups reached a mean LSI of >90% for peak torque (QT: 67.5% [95% CI, 64.8-70.1]; HT: 84.9% [95% CI, 82.4-87.4]; BPTB: 74.4% [95% CI, 72.0-76.9]). CONCLUSION: At 7 months after ACLR, patients with QT grafts had significantly worse isokinetic quadriceps strength than patients with HT and BPTB grafts. None of the 3 graft groups reached a mean LSI of >90% in quadriceps strength.

Editorial Commentary: Quadriceps Tendon Is a Better Graft Than Hamstring for Anterior Cruciate Ligament Reconstruction.

Over the last 12 years identification of specific risk factors (age, activity level, and laxity) for failure of anterior cruciate ligament (ACL) reconstruction have led to comparisons of the patellar tendon (PT) and hamstring (HS) tendon grafts. The PT has proved superior in most of these studies. During this same time period, there has been increased clinical/research interest in the quadriceps tendon autograft for ACL reconstruction. This has led to direct comparison to the HS and QT autografts. Again, the HS tendon appears inferior in measured outcomes to the quadriceps tendon. Increased laxity measurements seem to correlate with the decreased evidence of radiographic healing on magnetic resonance imaging. If this is the case, it may indeed be the final nail in the coffin for HS graft use in young at-risk athletic populations.

Estimation Failure Risk by 0.5-mm Differences in Autologous Hamstring Graft Diameter in Anterior Cruciate Ligament Reconstruction: A Meta-analysis.

BACKGROUND: Because grafts are made in 0.5-mm increments clinically for anterior cruciate ligament (ACL) reconstruction, it is important to clarify how the failure rate decreases as the diameter increases. Moreover, it is important to know whether even a slight increase in the graft diameter decreases the risk of failure. HYPOTHESIS: The risk of failure decreases significantly with each 0.5-mm increase in hamstring graft diameter. STUDY DESIGN: Meta-analysis; Level of evidence, 4. METHODS: The systematic review and meta-analysis have estimated the diameter-specific failure risk for each 0.5-mm increase in ACL reconstruction using autologous hamstring grafts. We searched for studies describing the relationship between graft diameter and failure rate published before December 1, 2021, in leading databases, such as PubMed, EMBASE, Cochrane Library, and Web of Science, according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We included studies using single-bundle autologous hamstring grafts to investigate the relationship between failure rate and graft diameter of 0.5-mm intervals with >1-year follow-up. Then, we calculated the failure risk caused by 0.5-mm differences in autologous hamstring graft diameter. Assuming Poisson distribution for the statistical model, we employed an extended linear mixed-effects model in the meta-analyses. RESULTS: Five studies containing 19,333 cases were eligible. The meta-analysis revealed that the estimated value of the coefficient of diameter in the Poisson model was -0.2357 with a 95% CI of -0.2743 to -0.1971 (P < .0001). With every 1.0-mm increase in diameter, the failure rate decreased by 0.79 (0.76-0.82) times. In contrast, the failure rate increased by 1.27 (1.22-1.32) times for each 1.0-mm decrease in diameter. The failure rate significantly decreased with each 0.5-mm increase in graft diameter in the range of <7.0 to >9.0 mm from 3.63% to 1.79%. CONCLUSION: The risk of failure decreased correspondingly with each 0.5-mm increase in graft diameter in the range of <7.0 to >9.0 mm. Failure is multifactorial; however, increasing the graft diameter as much as possible to match each patient's anatomic space without overstuffing is an effective precaution that surgeons can take to reduce failures.

Randomized Controlled Trials Comparing Bone-Patellar Tendon-Bone Versus Hamstring Tendon Autografts in Anterior Cruciate Ligament Reconstruction Surgery Are Statistically Fragile: A Systematic Review.

PURPOSE: To assess the statistical fragility of recently published randomized controlled trials (RCTs) comparing the use of hamstring tendon autograft with bone-patellar tendon-bone autograft for anterior cruciate ligament (ACL) reconstruction. METHODS: The PubMed, Embase, and MEDLINE databases were queried for RCTs published since 2010 comparing autograft type (bone-patellar tendon-bone vs hamstring tendon) in ACL reconstruction surgery. The fragility index (FI) and reverse FI (rFI) were determined for significant and nonsignificant outcomes, respectively, as the number of outcome reversals required to change statistical significance. The fragility quotient (FQ) and reverse FQ, representing fragility as a proportion of the study population, were calculated by dividing the FI and rFI, respectively, by the sample size. RESULTS: We identified 19 RCTs reporting 55 total dichotomous outcomes. The median FI of the 55 total outcomes was 5 (interquartile range [IQR], 4-7), meaning a median of 5 outcome event reversals would alter the outcomes' significance. Five outcomes were reported as statistically significant with a median FI of 4 (IQR, 2-6), meaning a median of 4 outcome event reversals would change outcomes to be nonsignificant. Fifty outcomes were reported as nonsignificant with a median rFI of 5 (IQR, 4-7), meaning a median of 5 outcome event reversals would change outcomes to be significant. The FQ and reverse FQ for significant and nonsignificant outcomes were 0.025 (IQR, 0.018-0.045) and 0.082 (IQR, 0.041-0.106), respectively. For 61.8% of outcomes, patients lost to follow-up exceeded the corresponding FI or rFI. CONCLUSIONS: There is substantial statistical fragility in recent RCTs on autograft choice in ACL reconstruction surgery given that altering a few outcome events is sufficient to reverse study findings. For over half of outcomes, maintaining patients lost to follow-up may have been sufficient to reverse study conclusions. CLINICAL RELEVANCE: We recommend co-reporting FIs and P values to provide a more comprehensive representation of a study's conclusions when conducting an RCT.

Evidence of Bacterial Metabolism in Synovial Fluid of Patients With Graft Failure After Anterior Cruciate Ligament Reconstruction: A Microbiological Comparison of Primary Anterior Cruciate Ligament and Hamstring Tendon Autograft Ruptures.

PURPOSE: To investigate whether the bacterial presence in a primary ruptured native anterior cruciate ligament (ACL) differs from that in a ruptured hamstrings ACL autograft and whether low-grade infections cumulatively can be detected in the case of graft failure. METHODS: In a retrospective case-control study with prospectively collected data, synovial fluid aspirates and tissue samples of failed ACL grafts were examined for evidence of bacterial colonization and compared to samples of the native ACL in primary ACL reconstruction (ACLR) using microbiological culture, 16S rRNA-PCR and histopathological examination. Furthermore, synovial fluid aspiration was investigated for possible future biomarkers for a low-grade infection. RESULTS: A total of 112 consecutive patients undergoing primary ACLR without history of previous surgeries to the affected knee (n = 59) and revision ACLR after reconstruction with a hamstring tendon autograft (n = 53) were recruited from one center. No patient had a history or showed clinical signs of infection. A total of 389 samples were analyzed by culture. Bacteria were detected in 9.4% of patients with a graft rupture (n = 5/53) compared to 3.4% of patients with a primary ACL rupture (n = 2/59) showing no statistical difference (P = .192). One patient with a "true" low-grade infection was found in our study population, resulting in a prevalence of 1.9% (1/53) in the graft group. The percentage of polymorphonuclear leukocytes (PMN%) as a highly sensitive marker for joint infections was significantly higher in aspirated synovial fluid of graft ruptures (27% ± 3% vs 20% ± 4%; P = .032), as well as glucose levels were significantly lower (83 mg/dL ± 2 mg/dL vs 88 mg/dL ± 2 mg/dL; P = .042). CONCLUSIONS: Synovial fluid obtained before revision ACLR showed a higher percentage of polymorphonuclear leukocytes and lower glucose levels compared with primary ACLR, suggesting bacterial metabolism and demonstrating that the intra-articular milieu changes significantly after ACLR. Tissue samples of ACL grafts revealed a low-grade infection in one case, although overall cultivable bacterial presence did not differ significantly when compared to samples of a native ACL. LEVEL OF EVIDENCE: Level III, retrospective case-control study.