Decreased Posterior Tibial Slope and Its Association With Pediatric Posterior Cruciate Ligament Injury.

BACKGROUND: Recent adult studies have demonstrated that decreased posterior tibial slope angle (PTSA) may be a risk factor for posterior cruciate ligament (PCL) injury. However, there is no study investigating this phenomenon in a pediatric population. Understanding risk factors for PCL injuries among a pediatric population is important given the recent rise in athletic competition/specialization and sports-related injuries. HYPOTHESIS/PURPOSE: The purpose of this study was to compare PTSA between pediatric patients sustaining a primary PCL tear compared with age- and sex-matched controls. It was hypothesized that pediatric patients sustaining a PCL tear would have a decreased PTSA compared with controls, with decreased PTSA being associated with higher odds of PCL injury. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: The records of all patients sustaining a PCL injury between 2006 and 2021 at a level 1 pediatric trauma center were reviewed. Patients aged ≤18 years with magnetic resonance imaging-confirmed PCL tear were included. Excluded were patients with concomitant anterior cruciate ligament tears, previous PCL reconstruction, or previous coronal plane realignment. A control cohort, with their ligament shown as intact on magnetic resonance imaging scans, was matched based on age and sex. PTSA was measured on lateral radiographs of the injured knee or tibia. The mean PTSA was compared between cohorts, and odds ratios were calculated based on the normal slope range (7°-10°) described in the literature, an upper range (>10°), and a lower range (<7°). Inter- and intrarater reliability were determined via calculation of an intraclass correlation coefficient. RESULTS: Of the 98 patients who sustained a PCL injury in this study period, 59 (60%) met inclusion criteria, and 59 healthy knee controls were matched. There were no differences between the cohorts for age (P = .90), sex (P > .99), or body mass index (P = .74). The PCL cohort had a lower mean ± SD PTSA compared with the control group (5.9°± 2.7° vs 7.3°± 4.3°; P = .03). PTSA <7° was associated with a 2.8 (95% CI, 1.3-6.0; P = .01) times risk of PCL tear. Conversely, PTSA >10° was associated with a 0.27 (95% CI, 0.09-0.81; P = .02) times risk of PCL tear. These PTSA measurements demonstrated acceptable intrarater and interrater reliability. CONCLUSION: PTSA <7° was associated with an increased odds of PCL injury, whereas a slope >10° was associated with a decreased odds of PCL injury in a pediatric population. These findings corroborate similar outcomes in adult studies; however, further studies are needed to elucidate PTSA as a risk factor for PCL injury.

Change in Posterior Tibial Slope Angle After Displaced Pediatric Tibial Tubercle Fracture: A Model for Growth Modulation in the ACL-Deficient Knee.

Background: Increased posterior tibial slope angle (PTSA) has been shown to be an important risk factor for anterior cruciate ligament (ACL) injury. PTSA modulation is not utilized routinely to reduce risk of primary rupture or graft failure. Displaced tibial tubercle (TT) fractures in the skeletally immature are associated with potential growth arrest and may be used as a model to study PTSA changes in this setting. Purpose/Hypothesis: To quantify the change in PTSA (ΔPTSA) after operative treatment of displaced TT fractures in skeletally immature patients. It was hypothesized that there would be a progressive decrease in PTSA after TT injury and that rate of ΔPTSA would be highest during peak growth velocity. Study Design: Case series; Level of evidence, 4. Methods: Included were 22 patients (n = 23 knees; mean chronological and bone age at injury, 14 years; 86% male) who underwent surgery for displaced TT fracture. PTSA was measured on lateral radiographs at time of surgery and subsequent follow-up, and bone age at the time of injury was determined using radiographic standards. The rate of ΔPTSA for individual patient, total cohort, and sex-based subgroup trends were determined via linear regression (degrees per month; positive value indicates relatively anterior). Individual patient regression coefficients were averaged into bone age cohorts. Results: Average follow-up was 17 months (range, 6-52 months). The mean PTSA was -12°± 2.4° at the time of injury, and the mean ΔPTSA for the cohort was 0.30°± 0.31° per month (range, -0.27° to 0.97° per month). Linear regression demonstrated a significant relationship between months postfixation and PTSA, demonstrating a ΔPTSA of 0.31° per month (95% confidence interval [CI], 0.24° to 0.38°; P < .001). The highest ΔPTSA was seen at bone age 14 years (mean, 0.58°± 0.44° per month). The mean absolute change in PTSA from injury to final follow-up was 4.1° (range, -3.4° to 21°). Conclusion: Our data suggested that PTSA becomes more anterior after operatively treated pediatric TT fractures and that ΔPTSA may be influenced by bone age. This concept may be useful in considering surgical modulation of excessive PTSA in the pediatric ACL-deficient knee.

A Dynamic Elbow Testing Apparatus for Simulating Elbow Joint Motion in Varying Shoulder Positions.

Purpose: To develop and evaluate the capabilities of a dynamic elbow testing apparatus that simulates unconstrained elbow motion throughout the range of humerothoracic (HTA) abduction. Methods: Elbow flexion was generated by six computer-controlled electromechanical actuators that simulated muscle action, while six degree-of-freedom joint motion was measured using an optical tracking device. Repeatability of joint kinematics was assessed at four HTA angles (0°, 45°, 90°, 135°) and with two muscle force combinations (A1-biceps brachialis, brachioradialis and A2-biceps, brachioradialis). Repeatability was determined by comparing kinematics at every 10° of flexion over five flexion-extension cycles (0° to 100°). Results: Multiple muscle force combinations can be used at each HTA angle to generate elbow flexion. Trials showed that the testing apparatus produced highly repeatable joint motion at each HTA angle and with varying muscle force combinations. The intraclass correlation coefficient was greater than 0.95 for all conditions. Conclusions: Repeatable smooth cadaveric elbow motion was created that mimicked the in vivo situation. Clinical relevance: These results suggest that the dynamic elbow testing apparatus can be used to characterize elbow biomechanics in cadaver upper extremities.

The Effect of Elbow Flexion On Valgus Carrying Angle.

PURPOSE: This study aimed to examine the effect of flexion on valgus carrying angle in the human elbow using a dynamic elbow testing apparatus. METHODS: Active elbow motion was simulated in seven cadaveric upper extremities. Six electromechanical actuators simulated muscle action, while 6 degrees-of-freedom joint motion was measured with an optical tracking system to quantify the kinematics of the ulna with respect to the humerus as the elbow was flexed at the side position. Repeatability of the testing apparatus was assessed in a single elbow over five flexion-extension cycles. The varus angle change of each elbow was compared at different flexion angles with the arm at 0° of humerothoracic abduction or dependent arm position. RESULTS: The testing apparatus achieved excellent kinematic repeatability (intraclass correlation coefficient, >0.95) throughout flexion and extension. All elbows decreased their valgus carrying angle during flexion from 0° to 90° when the arm was maintained at 0° of humerothoracic abduction. Elbows underwent significant total varus angle change from full extension of 3.9° ± 3.4° (P = .007), 7.3° ± 5.2° (P = .01), and 8.9° ± 7.1° (P = .02) at 60°, 90°, and 120° of flexion, respectively. No significant varus angle change was observed between 0° and 30° of flexion (P = .66), 60° and 120° of flexion (P = .06), and 90° and 120° of flexion (P = .19). CONCLUSIONS: The dynamic elbow testing apparatus characterized a decrease of valgus carrying angle during elbow flexion and found that most varus angle changes occurred between 30° and 90° of flexion. All specimens underwent varus angle change until at least 90° of flexion. CLINICAL RELEVANCE: Our model establishes the anatomic decrease in valgus angle by flexion angle in vitro and can serve as a baseline for testing motion profiles of arthroplasty designs and ligamentous reconstruction in the dependent arm position. Future investigations should focus on characterizing motion profile change as the arm is abducted away from the body.

Allograft Anterior Cruciate Ligament Reconstruction in Adolescent Patients May Result in Acceptable Graft Failure Rate in Nonpivoting Sports Athletes.

BACKGROUND: Studies have demonstrated that pediatric patients have an increased risk of failure with allograft anterior cruciate ligament reconstruction (ACLR); however, there is no study investigating whether allograft ACLR may be safe in older adolescent patients who are not returning to competitive pivoting sports (ie, low risk). The purpose of this study was to assess outcomes for low-risk older adolescents selected for allograft ACLR. METHODS: We performed a retrospective chart review of patients younger than 18 years who received a bone-patellar-tendon-bone allograft or autograft ACLR by a single orthopaedic surgeon from 2012 to 2020. Patients were offered allograft ACLR if they did not intend to return to pivoting sports for 1 year. The autograft cohort was matched 1:1 based on age, sex, and follow-up. Patients were excluded for skeletal immaturity, multiligamentous injury, prior ipsilateral ACLR, or concomitant realignment procedure. Patients were contacted to obtain patient-reported outcomes at ≥2 years follow-up, including single assessment numerical evaluation, surgery satisfaction, pain scores, Tegner Activity Scale, and the Lysholm Knee Scoring Scale. Parametric and nonparametric tests were used as appropriate. RESULTS: Of the 68 allografts, 40 (59%) met inclusion and 28 (70%) were contacted. Among the 456 autografts, 40 (8.7%) were matched and 26 (65%) were contacted. Two allograft patients (2/40; 5%) failed at a median (interquartile range) follow-up of 36 (12, 60) months. There were 0/40 failures in the autograft cohort and 13/456 (2.9%) among the overall autografts; neither were significantly different from the allograft failure rate (both P > 0.05). Two (5.0%) patients in the autograft cohort required manipulation under anesthesia and arthroscopic lysis of adhesions. There were no significant differences between cohorts for single assessment numerical evaluation, Lysholm, Tegner, pain, and satisfaction scores (all P > 0.05). CONCLUSIONS: Although ACL allograft failure rates remain nearly two times higher than autograft failure rates in older adolescents, our study suggests that careful patient selection can potentially bring this failure rate down to an acceptable level. LEVEL OF EVIDENCE: Level III; retrospective matched cohort study.

Surgical management of complex post-tuberculous kyphosis among African patients: clinical and radiographic outcomes for a consecutive series treated at a single institution in West Africa.

STUDY DESIGN: Retrospective review of consecutive series. OBJECTIVE: To assess the clinical and radiographic outcomes after surgical management of post-tuberculous kyphosis. Post-tuberculous (TB) kyphosis can lead to progressive pulmonary and neurological deterioration. Surgery is indicated to decompress neural elements and correct the spine deformity. Although posterior vertebral column resection (PVCR) has been established as the treatment of choice for severe TB kyphosis, there is paucity of studies on the clinical outcomes among patients treated in West Africa. METHODS: Clinical and radiographic data of 57 patients (pts) who underwent surgical correction of post-TB kyphosis at a single site in West Africa between 2013 and 2018 (≥ 2-year follow-up in 36 pts, ≥ 1-year FU in 21 pts). Pre- and post-op SRS scores and radiographic outcomes were compared using Paired t test. RESULTS: 57 patients, 36M:21F. Mean age 19 (11-57 years). 22/57 pts (39.3%) underwent pre-op halo gravity traction (HGT) for an average duration of 86 days (8-144 days). HGT pts had a higher baseline regional kyphosis (125.1 ± 20.9) compared to non-HGT pts (64.6 ± 31.8, p < 0.001). Post-HGT regional kyphosis corrected to 101.2 ± 23 (24° correction). 53 pts (92.9%) underwent posterior-only surgery and 4 (7.0%) combined anterior-posterior surgery. 39 (68.4%) had PVCR, 11 (19.3%) PSO, and 16 (28.1%) thoracoplasty. Intraoperative neuromonitoring (IOM) signal changes occurred in 23/57 pts (≈ 40%), dural tear in 5 pts (8.8%), pleural tear in 3 pts (5.3%), ureteric injury in 1 pt (1.7%), and vascular injury in 1 pt (1.7%). Post-op complications included four (7.0%) infection, three (5.3%) implant related, two (3.5%) radiographic (one PJK and one DJK), one (1.7%) neurologic, one (1.7%) wound problem, and two (3.5%) sacral ulcers. IOM changes were similar in the VCR (48.7%) and non-VCR (23.5%) pts, p > 0.05. Complication rates were similar among HGT and non-HGT groups. Significant improvements from baseline were seen in the average SRS Total and domains scores and radiographic measurements for patients who attained 2-year follow-up. CONCLUSION: PVCR ± HGT can provide safe and optimal correction in cases of severe post-TB kyphosis with good clinical and radiographic outcomes in underserved regions.

Elbow Biomechanics: Bony and Dynamic Stabilizers.

The elbow positions the hand in a stable manner relative to the trunk while allowing flexion and extension as well as forearm rotation at varying shoulder positions. Its ability to perform this task without joint subluxation is accomplished through a combination of bony congruency, ligamentous restraint, and dynamic stabilization. This article reviews the bony and dynamic contributors to elbow stability and kinematics. Bony stability is conferred through the morphology of the humeroulnar, humeroradial, and radioulnar joints. Depending on the arm position relative to the trunk and the degree of elbow flexion, the bony contribution will vary. Dynamic elbow stabilizers confer stability through the activation of various muscles that cross the elbow. These forces help resist valgus and varus forces and may also increase bony stability by generating compressive forces. The goal of this article is to review the literature surrounding the biomechanics of bony and dynamic stabilizers of the elbow while drawing clinically relevant biomechanical observations.

Elbow Biomechanics: Soft Tissue Stabilizers.

The elbow positions the hand in a stable manner relative to the trunk while allowing flexion and extension as well as forearm rotation at varying shoulder positions. Its ability to perform this task without joint subluxation is accomplished through a combination of bony congruency, ligamentous restraint, and dynamic stabilization. Elbow stability is challenged repeatedly during everyday activities, particularly when the arm is abducted. Traumatic injuries that lead to an elbow dislocation or the microtrauma associated with pitching are frequent situations that destabilize the elbow. This article reviews the soft tissue stabilizers that contribute to elbow kinematics and stability.