Reconstruction of the anterior cruciate ligament (ACL) allows to restore stability of the knee, in order to facilitate the return to activity (RTA). Although it is understood that the tendon autograft undergoes a ligamentous transformation postoperatively, knowledge about longitudinal microstructural differences in tissue integrity between types of tendon autografts (ie, hamstring vs. patella) remains limited.

Diffusion tensor imaging (DTI) has emerged as an objective biomarker to characterize the ligamentization process of the tendon autograft following surgical reconstruction. One major limitation to its use is the need for a pre-injury baseline MRI to compare recovery of the graft, and inform RTA. Here, we explore the relationship for DTI biomarkers (fractional anisotropy, FA) between knees bilaterally, in healthy participants, with the hypothesis that agreement within a patient's knees may support the use of the contralateral knee as a reference to monitor recovery of the tendon autograft, and inform RTA.

Fifteen participants with no previous history of knee injuries were enrolled in this study (age, 26.7 +/− 4.4 years; M/F, 7/8). All images were acquired on a 3T Prisma Siemens scanner using a secured flexible 18-channel coil wrapped around the knee. Both knees were scanned.

A 3D anatomical Double Echo Steady State (DESS) sequence was acquired on which regions of interest (ROI) were placed consistent with the footprints of the ACL (femur, posteromedial corner on medial aspect of lateral condyle; tibia, anteromedial to intercondylar eminence). Diffusion images were acquired using fat saturation based on optimized parameters in-house.

All diffusion images were pre-processed using the FMRIB FSL toolbox. The footprint ROIs of the ACL were then used to reconstruct the ligament in each patient with fiber-based probabilistic tractography (FBPT), providing a semi-automated approach for segmentation. Average FA was computed for each subject, in both knees, and then correlated against one another using a Pearson correlation to assess the degree of similarity between the ACLs.

A total of 30 datasets were collected for this study (1/knee/participant; N=15). The group averaged FA (+/− standard deviation) for the FBPT segmented ACLs were found to equal 0.1683 +/− 0.0235 (dominant leg) and 0.1666 +/− 0.0225 (non-dominant leg). When comparing both knees within subjects, reliable agreement was found for the FBPT-derived ACL with a linear correlation coefficient (rho) equal to 0.87 (P < 0 .001).

We sought to assess the degree of concordance in FA between the knees of healthy participants with hopes to provide a method for using the contralateral “healthy” knee in the comparison of autograft-dependent longitudinal changes in microstructural integrity, following ACL reconstruction. Our results suggest that good agreement in anisotropy can be achieved between the non-dominant and dominant knees using DTI and the FBPT segmentation method.

Contralateral anisotropy of the ACL, assuming no previous injuries, may be used as a quantitative reference biomarker for monitoring the recovery of the tendon autograft following surgical reconstruction, and gather further insight as to potential differences between chosen autografts. Clinically, this may also serve as an index to supplement decision-making with respect to RTA, and reduce rates of re-injuries.

The anterolateral ligament (ALL) is considered as an important stabilizer of the knee joint. This ligament prevents anterolateral subluxation of the proximal tibia on the femur when the knee is flexed and internally rotated. Injury of the ALL was not investigated in patients with knee dislocation. The aim of the current research is to study the prevalence and characteristics of ALL injury in dislocated knees.

A retrospective review of charts and radiological images was done for patients who underwent multiligamentous knee reconstruction surgery for knee dislocation in our institution from May 2008 to December 2016. Magnetic resonance imaging (MRI) was used to describe the ALL injury. The association of ALL injury with other variables related to the injury and the patient's background features was examined.

Forty-eight patients (49 knees) were included. The mean age of the patients was 32.3 ± 10.6 years. High energy trauma was the mechanism of dislocation in 28 (57.1%) knees. Thirty-one knees (63.3%) were classified as knee dislocation (KD) type IV. Forty-five (91.8%) knees had a complete ALL injury and three (6.1%) knees had incomplete ALL injury. Forty (81.6%) knees had a complete ALL injury at the proximal fibres of the ALL, while 23 (46.9%) knees had complete distal ALL injury. None of the 46 (93.9%) knees with lateral collateral ligament (LCL) injury had normal proximal ALL fibres (p = 0.012). Injury to the distal fibres of the ALL, as well as overall ALL injury, were not associated with any other variables (p >0.05). Moreover, all patients with associated tibial plateau fractures (9, 18.4%) had abnormality of the proximal fibres of the ALL (p = 0.033).

High grade ALL injury is highly prevalent among dislocated knees. The outcomes of reconstructing the ALL in multiligamentous knee reconstruction surgery should be investigated in future studies.

Several studies have highlighted the relationship between anterior cruciate (ACL) injury and knee geometry particularly tibial slope (TS). However, clinical data are inconsistent, whether the lateral or medial or slopes have a different influence on ACL injury. Our goal was to assess whether the medial, lateral slopes are associated with ACL injury and whether meniscus geometry is associated with ACL injury. In addition, we sought to determine if lateral meniscal height could serve as a simple surrogate measurement for ACL injury risk.

A case-controlled study compared 68 patients with an ACL injury and 68 matched nested controls. Radiological analysis of MRI measured the anterior-posterior distance of the medial and lateral plateaus, the tibial slope of both plateaus and meniscus geometry. Groups were compared using a Mann-Whitney test and α < 0 .05.

The lateral tibial plateau slope was significantly higher in the ACL injured group (6.92 degrees ±5.8) versus the control group 2.68 ±5.26 (p 0.0001). In addition, the lateral meniscal slope was significantly steeper with (ACL injuries: −1 ±4.7 versus −4.73 ±4.4 (p 0.0001) in the control group. The ACL Injured group had a significantly lower lateral meniscal height 0.76 cm ±0.09, compared to the control group that has 0.88 cm ±0.12 (p 0.0001). The Lateral meniscal height had a sensitivity of 76.47% and specificity 75% for predicting ACL injury using a cut off of

Patients with ACL-injury had significantly higher lateral tibial plateau slope. Lateral meniscus height was found to be an easy measurement to make on MRI with a high specificity for predicting ACL injury. Lateral tibial slope and meniscal Geometry can be used to identify patients with high risk of an ACL injury, that might benefit from further surgery to optimize rotational stability in high-risk patients.

Anterior cruciate ligament (ACL) injuries are frequent among athletes and a leading cause of time away from competition. Stability of the knee involves the ACL for limiting anterior tibial translation and the ALL (anterolateral ligament) to restrain internal rotation of the tibia. Present indications for treatment with a combined ACL-ALL reconstruction remain unclear and mostly subjective. We mathematically modeled the tibial plateau geometry to try and identify patients at risk of ACL injury, and develop an objective trigger point for the decision to proceed with additional surgery to optimize rotational stability in these higher risk patients. We hypothesized that an increased convexity and steepness of the posterior aspect of the lateral plateau would subject knees to higher rotational torques leading to potentially a higher risk of ACL injury.

The study design was a case-control study involving ACL reconstruction cases (n=68) and matched controls (n=68) between 2008–2015 at our institution. We used a two-dimensional approach, evaluating sagittal MRI images of the knee to model the posterior convexity of the lateral tibial plateau. Points were selected along the articular surface, and a least-squares regression was used to curve-fit a power function (y = a xn). In the equation, larger coefficient a and n represented steeper slopes. The cases and controls were compared using a Mann-Whitney-U test, and the statistical significance was set at α < 0.05. A subgroup analysis for females and males was also performed for the curve-fit coefficients.

We observed a significant difference in the tibial surface geometry between our ACL reconstruction cases and matched controls (Figure 1). The modeled power equation for our ACL cases had larger coefficients compared to controls for all groups. For all pooled subjects, coefficient a (ACL recon cases = 0.90 vs controls = 0.68, p < 0.0001) and coefficient n (ACL recon cases = 0.34 vs controls = 0.30, p = 0.07) (Table 1). For the statistically significant coefficient a, we found it had a sensitivity of 78.9% and specificity of 77.5% for the statistically significant coefficient a, we found it had a sensitivity of 78.9% and specificity of 77.5% for predicting injury, using a cut off coefficient of a = 0.78. The odds ratio was 12.6 [5.5 – 29].

The posterolateral cartilaginous slope of the tibial plateau was mathematically modeled in patients with ACL injury. Patients with ACL injury demonstrated abnormally steep and fast slopes compared to controls that may play predispose to ACL injury by increasing anterior translation forces and internal rotation torques sustained by their knee joint. A steeper slope may also explain high-grade pivot shifts on physical exam that are thought to be a relative indication for adding an associated ALL reconstruction. Our findings are promising for adding more objectivity to surgical decision-making, especially with identifying high-risk patients that may be candidates for combined ACL-ALL reconstructions.

For any figures or tables, please contact the authors directly.

Anterior shoulder instability is associated with osseous defects of the glenoid and/or humeral head (Hill-Sachs lesions). These defects can contribute to the pathology of instability by engaging together. There is a need to continue to develop methods to preoperatively identify engaging Hill-Sachs lesions for determining appropriate surgical management.

The objective was to created a working moveable 3D CT model that allows the user to move the shoulder joint into various positions to assess the relationship between the Hill-Sachs lesion and the anterior glenoid rim. This technique was applied to a cohort series of 14 patients with recurrent anterior dislocation: 4 patients had undergone osteoarticular allografting of Hill-Sachs lesions and 10 control patients had undergone CT scanning to quantify bone loss but had no treatment to address bony pathology. A biomechanical analysis was performed to rotate each 3D model using local coordinate systems through a functional range using an open-source 3D animation program, Blender (Amsterdam, Netherlands). A Hill-Sachs lesion was considered “dynamically” engaging if the angle between the lesion's long axis and anterior glenoid was parallel.

In the classical vulnerable position of the shoulder (abduction=90, external rotation=0–135), none of the Hill-Sachs lesions aligned with the anterior glenoid in any of our patients (Figure 1). Therefore, we considered there to be a “low risk” of engagement in these critical positions, as the non-parallel orientation represents a lack of true articular arc mismatch and is unlikely to produce joint instability. We then expanded our search and simulated shoulder positions throughout a physiological range of motion for all groups and found that 100% of the allograft patients and 70% of the controls had positions producing alignment and were “high risk” of engagement (p = 0.18) (Table 1). We also found that the allograft group had a greater number of positions that would engage (mean 4 ± 1 positions of engagement) compared to our controls (mean 2 ± 2 positions of engagement, p = 0.06).

We developed a 3D animated paradigm to dynamically and non-invasively visualize a patient's anatomy and determine the clinical significance of a Hill-Sachs lesion using open source software and CT images. The technique demonstrated in this series of patients showed multiple shoulder positions that align the Hill-Sachs and glenoid axes that do not necessarily meet the traditional definition of engagement. Identifying all shoulder positions at risk of “engaging”, in a broader physiological range, may have critical implications towards selecting the appropriate surgical management of bony defects. We do not claim to doubt the classic conceptual definition of engagement, but we merely introduce a technique that accounts for the dynamic component of shoulder motion, and in doing so, avoid limitations of a static criteria assumed traditional definition (like size and location of lesion). Further investigations are planned and will help to further validate the clinical utility of this method.

For any figures or tables, please contact the authors directly.

Aims

Computer-based applications are increasingly being used by orthopaedic surgeons in their clinical practice. With the integration of technology in surgery, augmented reality (AR) may become an important tool for surgeons in the future. By superimposing a digital image on a user’s view of the physical world, this technology shows great promise in orthopaedics. The aim of this review is to investigate the current and potential uses of AR in orthopaedics.

Purpose: The goal was to determine whether locking screws (LS) or smooth locking pegs (SP), optimize fixation of 4-part intraarticular distal radius fractures. The secondary goal was to determine which combinations of LS and SP influence construct stability.

Method: In anatomic radius models, 4-part intraarticular distal radius fractures were fixed using volar locking plates. For the first part, 16 specimens were randomized to receive either 2 LS or 2 SP in each of the 3 pairs of holes in the plate. For the second part, 30 specimens were randomized to receive any 4 combinations of LS and SP in each of the 3 pairs of holes. Axial loading to failure was applied.

Results: Constructs consisting of 4 SP within the lunate fragment were significantly weaker than constructs with 4 LS (mean 626.18 N vs. mean 980.76 N, p=0.01283). Constructs with SP in the ulnar positions of the lunate fragment were weaker than with LS in these positions (mean 736.73 N vs. 977.37 N respectively, p=0.00866). LS in the subchondral position of the lunate fragment were stronger than SP in these positions (mean 1226.99 N vs. 933.64 N, p= 0.00468) and any other combination (mean 1226.99 N vs. 941.97 N, p=0.0027).

Conclusion: The use of LS as opposed to SP for 4-part intraarticular distal radius fractures, particularly subchondral and in ulnar side of the lunate fragment, optimizes construct stability. This may have implications on postoperative rehabilitation protocols and may limit costs related to the use of volar locking plates.

Purpose: Tibial slope is an important contributor to sagittal plane stability. Anterior opening wedge high tibial osteotomy (HTO) has received increased attention for sagittal plane correction. A previous study demonstrated that anterior opening wedge HTO induced no increased strain in the ACL [1]. The goal of this present study was to determine the effect of increasing tibial slope on the strains of the major ligamentous restraints of the knee and on the change in position of the tibia in relation to the femur.

Method: Six cadaveric knee specimens were mounted at 15 degrees of flexion in a testing apparatus providing both compressive and anterior loading. Strains were measured in the ACL, PCL, MCL, and LCL for six randomized loading combinations and 3 conditions: intact, after anterior opening wedge HTO with 5mm plate, and 10mm plate. Tibial translation, rotation measurements and tibial slopes were obtained for each test.

Results: ACL strain was significantly associated with the plating intervention (p< 0.001). ACL strain decreased from −0.66 +/− 1.48 at baseline to −7.44 +/− 6.60 with a 5mm anterior opening wedge HTO and −7.99 +/− 6.45 with a 10mm osteotomy. Stepwise regressions yielded no significant effect of compression, anterior loading or osteotomy or combination thereof on PCL, MCL or LCL strain. Tibial slope and external rotation were significantly correlated with the plating intervention (p< 0.001 for both).

Conclusion: Increasing posterior slope via HTO did not increase strain in any of the major ligamentous restraints of the knee. Increasing tibial slope in the setting of a ligamentous deficient knee can be performed to increase stability without fear of submitting ligaments to increased strain.