Novel measurement technique of the tibial slope on conventional MRI

Influence of cartilage and menisci on the sagittal slope of the tibial plateaus

We analyzed the magnetic resonance studies of the knee in 80 subjects, 45 men and 35 women with a mean age of 38.9 years, who showed no pathological condition of the joint. Using an imaging visualization software, the sagittal longitudinal axis of the tibia was identified. The angle between this axis and a line tangent to the bone profile of the tibial plateau (bone slope) and to the superior border of the menisci (meniscal slope) were calculated. Thickness of anterior and posterior portion of menisci and underlying cartilage were also measured. The bone slope averaged 8° and 7.7° on the medial and lateral sides, respectively. The mean meniscal slope was 4.1° and 3.3° on the medial and lateral sides, respectively, with a significant difference compared with the bone slope. Menisci and underlying cartilage were significantly thicker in their posterior than their anterior portion (7.6 and 5.2 mm, respectively, in the medial compartment; 8.6 and 5.2 mm, respectively, in the lateral compartment). The presence of cartilage and menisci implies a significant decrease in the posterior tibial slope. In the lateral compartment, the greater the bone slope, the larger the difference between bone and meniscal slope, which means that a marked posterior tilt of the lateral tibial plateau is decreased by the cartilage and meniscus. These findings should be taken into account in planning surgical procedures which affect the slope of the articular tibial surface.

Computer navigation vs extramedullary guide for sagittal alignment of tibial components: radiographic study and meta-analysis

Sagittal alignment of tibial components using computer navigation was compared with conventional methods. A radiologic study was performed using 110 total knee arthroplasties from 3 groups: computer navigation, cutting block with extramedullary guide, and manual tilt of extramedullary guide. Posterior tibial slopes were measured from radiographs and compared using statistical methods. The cutting block method was the most accurate, and computer navigation was the most precise. The manual tilt group had the greatest variance, significantly greater than computer navigation. There was no significant difference between groups with respect to the percentage of knees with posterior slope within 3° of the desired slope. Meta-analysis of 10 studies found no reduction in outliers with computer navigation. Computer navigation offers greatest precision but does not reduce the number of outliers.

Morphologic characteristics help explain the gender difference in peak anterior cruciate ligament strain during a simulated pivot landing

BACKGROUND

Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading.

HYPOTHESIS

Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle tensile stiffness. Peak relative strain in the anteromedial bundle of the ACL (AM-ACL) was measured using a differential variable reluctance transducer, while ACL cross-sectional area and lateral tibial slope were measured using magnetic resonance imaging. A repeated-measures Mann-Whitney signed-rank test was used to test the hypothesis.

RESULTS

Female knees exhibited 95% greater peak AM-ACL relative strain than male knees (6.37% [2.53%] vs 3.26% [1.89%]; P = .004). Anterior cruciate ligament cross-sectional area and lateral tibial slope were significant predictors of peak AM-ACL relative strain (R(2) = .59; P = .001).

CONCLUSION

Peak AM-ACL relative strain was significantly greater in female than male knees from donors of the same height and weight. This gender difference is attributed to a smaller female ACL cross-sectional area and a greater lateral tibial slope.

CLINICAL RELEVANCE

Since female ACLs are systematically exposed to greater strain than their male counterparts, training and injury prevention programs should take this fact into consideration.

Development and validation of a new method for the radiologic measurement of the tibial slope

PURPOSE

The posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography.

METHODS

Fourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAA = tibial proximal anatomical axis; ATC = anterior tibial cortex; PTC = posterior tibial cortex) and the new computed reference (MPA = mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed.

RESULTS

CT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan (r = 0.997), even on short radiographs (10 cm distal the joint line).

CONCLUSION

The measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

Sagittal plane deformity in bicondylar tibial plateau fractures

OBJECTIVE

To evaluate the prevalence and magnitude of sagittal plane deformity in bicondylar tibial plateau fractures.

DESIGN

Retrospective radiographic review.

SETTING

Two Level I trauma centers.

MAIN OUTCOME MEASUREMENT

Sagittal inclination of the medial and lateral plateau measured in relation to the longitudinal axis of the tibia using computed tomographic reconstruction images.

PATIENTS

Seventy-four patients (mean age, 49 years; range, 16-82 years; 64% male) with acute bicondylar tibial plateau fractures (Orthopaedic Trauma Association 41C, Schatzker VI) treated from October 2006 to July 2009.

RESULTS

The average sagittal plane angulation of the lateral plateau was 9.8° posteriorly (range, 17° anteriorly to 37° posteriorly). The medial plateau was angulated 4.1° posteriorly on average (range, 16° anteriorly to 31° posteriorly). Forty-two lateral plateaus were angulated more than 5° from the "normal" anatomic slope (defined as 5° of posterior tibial slope). Of these, 76% were angulated posteriorly. Forty-three (58%) of the medial plateaus were angulated greater than 5° from normal, of which only 47% were inclined posteriorly (P = 0.019 compared with lateral plateaus). In 68% of patients, the difference between medial and lateral plateaus was greater than 5°; the average intercondylar slope difference was 9° (range, 0°-31°; P < 0.001). Spanning external fixation did not affect the slope of either the medial or lateral tibial plateau. Intraobserver and interobserver correlations were high for both the medial and lateral plateaus (r > 0.81, P < 0.01).

CONCLUSIONS

Considerable sagittal plane deformity exists in the majority of bicondylar tibial plateau fractures. The lateral plateau has a higher propensity for sagittal angulation and tends to have increased posterior slope. Most patients have a substantial difference between the lateral and medial plateau slopes. The identification of this deformity allows for accurate preoperative planning and specific reduction maneuvers to restore anatomic alignment.

Is noncontact ACL injury associated with the posterior tibial and meniscal slope?

BACKGROUND

The risk of noncontact ACL injury reportedly is increased in patients with a greater posterior tibial slope (PTS), but clinical data are inconsistent. It is unclear whether the medial and lateral PTSs have a different impact on this connection. It also is unknown whether the meniscal slope (MS) is associated with ACL injury.

PATIENTS/METHODS

Using MRI, we compared the medial and lateral PTSs and MSs separately in 55 matched pairs of patients with isolated noncontact ACL injuries and a control group.

RESULTS

Neither the PTS nor the relative difference between the medial and lateral PTSs differed between groups. In contrast, the lateral MS was greater with ACL injuries: 2.0° versus -2.7° in males with and without ACL injury and 1.7° versus -0.9 in females. Uninjured females had a greater PTS than males: 4.9° versus 3.0° in females and males medially, respectively; 5.7° versus 4.0° lateral.

CONCLUSIONS

There is no obvious link between the medial or lateral PTSs and ACL injury, and there is no obvious link between the relative difference in the medial and lateral PTSs and noncontact ACL injury. However, a greater lateral MS may indicate a greater risk of injury. The PTS can differ between the genders but the average difference is small.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

The relationship between anterior tibial acceleration, tibial slope, and ACL strain during a simulated jump landing task

BACKGROUND

Knee joint morphology contributions to anterior cruciate ligament (ACL) loading are rarely considered in the injury prevention model. This may be problematic as the knee mechanical response may be influenced by these underlying morphological factors. The goal of the present study was to explore the relationship between posterior tibial slope (which has been recently postulated to influence knee and ACL loading), impact-induced anterior tibial acceleration, and resultant ACL strain during a simulated single-leg landing.

METHODS

Eleven lower limb cadaveric specimens from female donors who had had a mean age (and standard deviation) of 65 ± 10.5 years at the time of death were mounted in a testing apparatus to simulate single-limb landings in the presence of pre-impact knee muscle forces. After preconditioning, specimens underwent five impact trials (mean impact force, 1297.9 ± 210.6 N) while synchronous three-dimensional joint kinetics, kinematics, and relative anteromedial bundle strain data were recorded. Mean peak tibial acceleration and anteromedial bundle strain were quantified over the first 200 ms after impact. These values, along with radiographically defined posterior tibial slope measurements, were submitted to individual and stepwise linear regression analyses.

RESULTS

The mean peak anteromedial bundle strain (3.35% ± 1.71%) was significantly correlated (r = 0.79; p = 0.004; ß = 0.791) with anterior tibial acceleration (8.31 ± 2.77 m/s-2), with the times to respective peaks (66 ± 7 ms and 66 ± 4 ms) also being significantly correlated (r = 0.82; p = 0.001; ß = 0.818). Posterior tibial slope (mean, 7.6° ± 2.1°) was significantly correlated with both peak anterior tibial acceleration (r = 0.75; p = 0.004; ß = 0.786) and peak anteromedial bundle strain (r = 0.76; p = 0.007; ß = 0.759).

CONCLUSIONS

Impact-induced ACL strain is directly proportional to anterior tibial acceleration, with this relationship being moderately dependent on the posterior slope of the tibial plateau.

Predicting ACL rupture in the population actively engaged in sports activities based on anatomical risk factors

The purposes of this article were identification (ie, verification and gradation) of anatomical risk factors that lead to anterior cruciate ligament (ACL) injury and determination of the probability of ACL injury among the population actively engaged in sports activities. We evaluated 66 patients divided into 2 groups: 33 patients in the examined group diagnosed with ACL lesion, and 33 patients in the control group diagnosed with patellofemoral pain. Patients were matched by age, sex, type of lesion, and whether the lesion was left or right sided. Measurements were carried out by radiography and magnetic resonance imaging. The study examined 32 anatomical factors. After identifying factors that lead to ACL injury, the following were determined: the coefficient of significance for each individual factor via the discriminant analysis and the canonical discriminant (i.e., canonical correlation). Fifteen factors in men and 8 factors in women were differentiated as having influence on ACL injury. Based on these factors, it was determined whether the patients belonged to the examined or the control group with a success rate of 100% in men (100% sensitivity and specificity) and 91.7% in women (100% sensitivity and 83.3% specificity). The anatomy of the ACL prone to rupture and of the skeletal structures influencing it is significantly different from the anatomy of the ACL ligament resistant to injury. The probability of precise prognosis of ACL injury based on differentiated anatomical factors is 88.9% in men and 75.7% in women actively engaged in sports activities.

Risk factors for anterior cruciate ligament injury: assessment of tibial plateau anatomic variables on conventional MRI using a new combined method

PURPOSE

The purpose of this study was to assess, in anterior cruciate ligament (ACL)-injured and -uninjured population, tibial plateau anatomic variables [medial and lateral tibial plateau slopes (MTPS and LTPS) and medial tibial plateau depth (MTPD)] on conventional magnetic resonance imaging (MRI) using a novel combined method and to determine whether these variables are risk factors for ACL injury.

METHODS

Seventy-three isolated ACL-injury patients (20 women and 53 men) were compared with 51 control group patients (19 women and 32 men).

RESULTS

The combined method had very high interrater and intrarater reliability compared with previously described methods. LTPS was significantly steeper in the overall injured group and injured men compared with the control group, with odds ratio (OR) of 3.031 and 5.89, respectively. Women with ACL injury had significantly shallower MTPD than uninjured women, with OR of 4.13.

CONCLUSIONS

We conclude that the new combined method is accurate and reproducible for assessing the tibial plateau anatomy. Women with shallower MTPD and men with steeper LTPS are at higher risk of sustaining ACL injury. Overall, steeper LTPS is a significant risk factor for sustaining ACL injury.

Lateral unicompartmental knee arthroplasty: a review

Lateral unicondylar knee arthroplasty (UKA) has been utilized as a treatment for isolated lateral tibiofemoral osteoarthritis (OA) since the first description of UKA in the 1970s. To date, there remains some controversy on UKA procedures. As indications for lateral UKA are usually rare, surgeon experience seems to be the key factor for a successful intervention. Better understanding of biomechanics of the knee joint, recent developments in prosthesis design, surgical techniques and indications may add to improved outcomes of lateral UKA. Alternatives that are applied to treat lateral tibiofemoral OA include arthroscopic interventions, osteotomies and total knee arthroplasty (TKA). In comparison with TKA, potential advantages of UKA include a minimally or less invasive approach, less bone resection, preservation of the cruciate ligaments, preservation of the medial tibiofemoral and the patellofemoral compartments, shorter rehabilitation, and physiological knee kinematics. This review aims to summarize the current concepts of implant designs as well as indications and contraindications for lateral UKA. The literature will be presented and discussed as well as results and realistic expectations on both the surgeon's and the patient's side. Alternative treatments and future concepts for lateral UKA will be presented.