Lateral extra-articular tenodesis does not enhance ACL graft healing, however, does reduce graft tunnel widening.

PURPOSE: The study hypothesized that the addition of lateral extra-articular tenodesis (LEAT) in anterior cruciate ligament reconstruction (ACLR) had a significant effect on ACL graft healing. METHODS: A total of 80 patients were divided into two cohorts matched for gender, age, body mass index, time from surgery to post-operative MRI and graft diameter. Forty patients underwent ACL reconstruction alone, while 40 underwent ACLR in addition to LEAT. Patients underwent a magnetic resonance imaging scan at 12 months post-surgery; tunnel apertures were measured using multiplanar reformation, graft healing was assessed using signal-to-noise quotient (SNQ) in three regions of interest and finally graft maturity and integration were classified using the Howell and Ge scale, respectively. In addition, clinical evaluation and patient-reported outcome measures were collected. RESULTS: The mean femoral tunnel widening at 12 months post-surgery was 39.8 ± 14.0% in the ACLR + LEAT group and 55.2 ± 12.7% in the ACLR alone group (p < 0.05). The mean tibial tunnel widening was 29.3 ± 12.7% in the ACLR + LEAT group and 44.4 ± 12.1% in the ACLR group (p < 0.05). The mean adjusted graft SNQ was 9.0 ± 14.9 in the ACLR + LEAT group and 9.5 ± 11.4 in the ACLR group (n.s.). CONCLUSION: At 1 year post-operatively, we noted significantly less femoral and tibial tunnel widening in the ACLR + LEAT group. LEAT did not result in a statistically significant effect on graft healing. LEVEL OF EVIDENCE: Level III.

Large multiplanar changes to native alignment have no apparent impact on clinical outcomes following total knee arthroplasty.

PURPOSE: This study sought to examine if achieved postoperative alignment when compared to the native anatomy would lead to a difference in Patient Reported Outcome Measures (PROMs), and whether the achieved alignment could be broadly categorised by an accepted alignment strategy. METHODS: A retrospective cohort study of prospectively collected data on patients undergoing single primary or bilateral simultaneous total knee arthroplasty (TKA) was carried out. CT scans were used to determine the mean change ("delta values") between the pre and postoperative; hip-knee-ankle angle, lateral distal femoral angle, medial proximal tibial angle and femoral implant rotation. Femoral implant flexion and tibial implant slope were measured postoperatively. The primary outcome was the relationship of the variables to the change in KOOS pain subscale after one year. The secondary outcome was the number of knees which could be categorised postoperatively to an alignment strategy, and the mean PROMs in each cohort. RESULTS: A total of 296 knees in 261 patients were available for analysis. With regards to the primary outcome, the delta values for each variable did not demonstrate any association with the change in knee injury and osteoarthritis outcome score (KOOS) pain score. Approximately 46% of knees could not be categorised to an alignment strategy based on postoperatively measured alignment, with no significant difference between each cohort with regards to the change in KOOS Pain score. CONCLUSION: Achieved alignment does not consistently match accepted alignment strategies, and appears to confer no benefit to clinical outcomes when the native anatomy is most closely approximated, nor results in poorer outcomes in outliers. This study highlights the importance of routine three dimensional pre and postoperative imaging in clinical practice and for the valid analysis of outcomes in studies on alignment. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

A balance between native footprint coverage and overlap of the anterolateral meniscal root in tibial tunnel positioning during anterior cruciate ligament reconstruction: A 3D MRI study.

BACKGROUND: Tibial footprint of anterior cruciate ligament (ACL) is situated close to the anterior lateral meniscal root (ALMR) attachment. PURPOSE: To investigate the impact of the size and location of the tibial tunnel for ACL reconstruction on the ACL footprint coverage and overlap to the ALMR. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty knee MRI scans from twenty healthy subjects were recruited, and three-dimensional (3D) tibia models were created to show the tibial attachment sites of ACL and ALMR. Surgical simulation of the tibial tunnel drilling was performed on each 3D model, entering the joint at an angle set at 60 degrees from the tibial plateau plane and 55 degrees from the posterior tibial condylar axis, with analysis for six different drill sizes; 7.5, 8, 8.5, 9, 9.5 and 10 mm; and nine locations; the center of the ACL attachment and eight locations 2% of the tibial width apart surrounding it. The width of the tibial plateau, the distance between ACL and ALMR attachment centers, and the size and location of the potential tibial tunnel were evaluated to determine association with the area of the ACL footprint coverage and ALMR overlap using a linear mixed effects model. RESULTS: A large tunnel (p <.001), a central and anterior location (p <.029), and small tibial width (p =.015) were all associated with larger coverage of the ACL footprint. A large tunnel (p <.001), posteriorly and laterally located (p ≤ 0.001), and a small distance between the ACL and ALMR centers (p =.001) were significantly associated with a larger ALMR overlap. The association of the tunnel size to ALMR overlap reduced with a medial tunnel location. CONCLUSIONS: The short distance between the centers of the ALMR attachment and native ACL footprint suggests that the ALMR will always be susceptible to overlap when the tibial tunnel is drilled in ACL reconstruction. Small alterations in tunnel location can lead to a statistically significant alteration with the amount of ALMR overlap. To minimize this overlap, whilst maintaining acceptable coverage of the ACL footprint, a tibial tunnel positioned in a medial or anteromedial location from the center of the ACL footprint is recommended.

Lower-limb muscle function in healthy young and older adults across a range of walking speeds.

BACKGROUND: Previous studies have compared the functional roles of the individual lower-limb muscles when healthy young and older adults walk at their self-selected speeds. No age-group differences were observed in ankle muscle forces and ankle muscle contributions to support and progression. However, older adults displayed higher gluteus maximus (hip extensor) muscle forces and greater contributions to support during early stance. There are no data that describe the functions of the individual lower-limb muscles in healthy older adults for walking at speeds other than the self-selected speed. RESEARCH QUESTION: How does walking speed affect the functional roles of the individual lower-limb muscles in healthy older adults? METHODS: Three-dimensional gait data were recorded for 10 healthy young and 10 healthy older adults walking at slow, normal, and fast speeds (0.7 m/s, 1.4 m/s, and 1.7 m/s, respectively). Both groups walked at the same speed at each condition. The experimental data were combined with a full-body musculoskeletal model to calculate and compare muscle forces and muscle contributions to the vertical, fore-aft, and mediolateral ground reaction forces (support, progression, and balance, respectively) in both groups. RESULTS: Lower-limb muscle function was similar in young and older adults when both groups walked at the same speed at each condition. The same five muscles - gluteus maximus, gluteus medius, vasti, gastrocnemius, and soleus - contributed most significantly to support, progression, and balance in both groups at all speeds. However, gluteus maximus generated greater support and braking forces during early stance and gastrocnemius contributed less to forward propulsion during late stance at all speeds in the older group. SIGNIFICANCE: These results provide further insight into the functional roles of the individual lower-limb muscles of older adults during walking and could inform the design of exercise programs aimed at improving support and balance in those at risk of falling.

Effects of step length and step frequency on lower-limb muscle function in human gait.

The aim of this study was to quantify the effects of step length and step frequency on lower-limb muscle function in walking. Three-dimensional gait data were used in conjunction with musculoskeletal modeling techniques to evaluate muscle function over a range of walking speeds using prescribed combinations of step length and step frequency. The body was modeled as a 10-segment, 21-degree-of-freedom skeleton actuated by 54 muscle-tendon units. Lower-limb muscle forces were calculated using inverse dynamics and static optimization. We found that five muscles - GMAX, GMED, VAS, GAS, and SOL - dominated vertical support and forward progression independent of changes made to either step length or step frequency, and that, overall, changes in step length had a greater influence on lower-limb joint motion, net joint moments and muscle function than step frequency. Peak forces developed by the uniarticular hip and knee extensors, as well as the normalized fiber lengths at which these muscles developed their peak forces, correlated more closely with changes in step length than step frequency. Increasing step length resulted in larger contributions from the hip and knee extensors and smaller contributions from gravitational forces (limb posture) to vertical support. These results provide insight into why older people with weak hip and knee extensors walk more slowly by reducing step length rather than step frequency and also help to identify the key muscle groups that ought to be targeted in exercise programs designed to improve gait biomechanics in older adults.

Muscle function during gait is invariant to age when walking speed is controlled.

Older adults walk more slowly, take shorter steps, and spend more time with both legs on the ground compared to young adults. Although many studies have investigated the effects of aging on the kinematics and kinetics of gait, little is known about the corresponding changes in muscle function. The aim of this study was to describe and compare the actions of the lower-limb muscles in accelerating the body's center of mass (COM) in healthy young and older adults. Three-dimensional gait analysis and subject-specific musculoskeletal modeling were used to calculate lower-limb muscle forces and muscle contributions to COM accelerations when both groups walked at the same speed. The orientations of all body segments during walking, except that of the pelvis, were invariant to age when these quantities were expressed in a global reference frame. The older subjects tilted their pelves more anteriorly during the stance phase. The mean contributions of the gluteus maximus, gluteus medius, vasti, gastrocnemius and soleus to the vertical, fore-aft and mediolateral COM accelerations (support, progression and balance, respectively) were similar in the two groups. However, the gluteus medius contributed significantly less to support (p<0.05) while the gluteus maximus and contralateral erector spinae contributed significantly more to balance (p<0.05) during early stance in the older subjects. These results provide insight into the functional roles of the individual leg muscles during gait in older adults, and highlight the importance of the hip and back muscles in controlling mediolateral balance.