Risk of tibial baseplate loosening is low in patients following unrestricted kinematic alignment total knee arthroplasty using a cruciate-retaining medial conforming insert: A study using radiostereometric analysis at 2 years.

PURPOSE: Assessing the risk of tibial baseplate loosening in patients after unrestricted kinematically aligned (unKA) total knee arthroplasty (TKA) using a medially conforming insert is important because baseplates generally are aligned in varus which has been linked to an increased incidence of aseptic loosening following mechanically aligned TKA. Two limits that indicate long-term stability in patients are a change in maximum total point motion between 1 and 2 years (ΔMTPM) < 0.2 mm and anterior tilt at 2 years < 0.8°. The purposes were to determine: (1) the number of patients with ΔMTPM > 0.2 mm, (2) the number of patients with anterior tilt > 0.8° and (3) whether increased varus baseplate and limb alignment were associated with increased migration. METHODS: Thirty-five patients underwent cemented, caliper-verified, unKA TKA using a medially conforming tibial insert with posterior cruciate ligament (PCL) retention. Biplanar radiographs acquired on the day of surgery and at 1.5, 3, 6, 12 and 24 months were processed with model-based radiostereometric analysis (RSA) software to determine migration and the number of patients with migration above the two stability limits. Medial proximal tibial angle (MPTA), hip-knee-ankle angle (HKAA) and posterior slope angle (PSA) were analyzed for an association with migration in six degrees of freedom and in MTPM. RESULTS: Thirty-two of 35 patients were available for analysis at 2 years. One patient exhibited ΔMTPM > 0.2 mm. The same patient exhibited anterior tilt > 0.8°. Varus rotation (p = 0.048, r ≤ 0.34) and medial translation (p = 0.0273, r ≤ 0.29) increased with increased varus baseplate alignment. CONCLUSION: The results indicate low risk of long-term baseplate loosening in patients. Although varus rotation and medial translation increased with increased varus baseplate alignment, the magnitudes of the migrations were minimal and did not increase ΔMTPM and anterior tilt. LEVEL OF EVIDENCE: Level II, therapeutic prospective cohort study.

Low tibial baseplate migration 1 year after unrestricted kinematically aligned total knee arthroplasty using a medial conforming implant design.

PURPOSE: Varus alignment of the tibial baseplate and limb > 3° might adversely affect baseplate fixation after total knee arthroplasty (TKA), especially for unrestricted kinematically aligned (KA) TKA which aligns a majority of baseplates in varus. The purposes of this study were to determine whether baseplate migration at 1 year (1) was significantly less than a stability limit of 0.5 mm, (2) increased over time, and (3) was related to varus alignment of the baseplate and limb after unrestricted KA TKA. METHODS: Thirty-five patients underwent unrestricted KA TKA using a fixed-bearing, cemented, medial conforming tibial insert with posterior cruciate ligament retention. Using model-based radiostereometric analysis, maximum total point motion (MTPM) (i.e., largest displacement on the baseplate) was computed at 6 weeks, 3 months, 6 months, and 1 year postoperatively relative to the day of surgery. Baseplate and limb alignment were measured postoperatively on long-leg CT scanograms. RESULTS: At 1 year, mean MTPM of 0.35 mm was significantly less than the 0.5 mm stability limit (p = 0.0002). Mean MTPM did not increase from 6 weeks to 1 year (p = 0.3047). Notably, 89% (31/35) of tibial baseplates and 46% (16/35) of limbs were > 3° varus. Baseplate and limb alignment had no relationship to MTPM at 1 year (|r|≤ 0.173, p ≥ 0.3276). CONCLUSION: Low and non-progressive tibial baseplate migration 1 year after unrestricted KA TKA with a medial conforming design should allay any concern that unrestricted KA TKA increases risk of baseplate loosening due to varus alignment of the baseplate and limb. LEVEL OF EVIDENCE: Level II, therapeutic prospective cohort study.

Fingertip light touch contact increases anteroposterior limits of stability in healthy young and older adults.

BACKGROUND: The limit of stability (LoS), an index of stance balance ability, is reduced in older adults. Although contacting an earth-fixed external surface through fingertips' light touch improves older adults' stance balance control, its effects on the LoS in this population are unclear. RESEARCH QUESTION: Does light touch increase the LoS and reduce postural sway in the LoS? METHODS: This study included 20 young adults (11 women and 9 men, mean age = 20.6 years) and 15 community-dwelling older adults (8 women and 7 men, mean age = 74.5 years). The position and path length of the center of pressure (CoP) during quiet standing (QS) and the anterior and posterior LoS (A-LoS and P-LoS, respectively) were measured using a force platform under two touch conditions (no-touch condition and light-touch condition). In light-touch condition, participants placed the tip of their dominant index finger on a load cell, which had an applied force of <1 N. RESULTS: In both touch conditions, the older group had a more limited CoP position in the anteroposterior LoS and a longer CoP path length in the QS and LoS than the younger group. In both participant groups, the light-touch condition showed a wider CoP position in the anteroposterior LoS and a shorter CoP path length in the QS and LoS than the no-touch condition. SIGNIFICANCE: Light touch increases the anteroposterior LoS and decreases postural sway in the LoS. Therefore, contacting an external object by fingertips' light touch may be an effective training protocol to increase the LoS in older adults.

Quiet standing and anteroposterior limits of stability in adolescents and young adults with bilateral spastic cerebral palsy.

Stance stability in individuals with bilateral spastic cerebral palsy (BSCP) in various standing postures including the quiet standing (QS) and limits of stability (LoS) has been widely studied. However, the relationships between the QS and LoS remain unclear. This study aimed to determine the relationships between the positions and postural sway in the QS and anteroposterior LoS in individuals with BSCP. It included 27 adolescents and young adults with BSCP (BSCP group) and 27 adolescents and young adults without disability (control group). The position of center of pressure in the anteroposterior direction (CoPy position) and the path length of center of pressure (CoP path length) during the QS and the anterior and posterior LoS (A-LoS and P-LoS, respectively) were measured using a force platform. The CoPy positions in the A-LoS and P-LoS in the BSCP group were limited compared with those in the control group. In the BSCP group, the more anterior the CoPy position in the QS, the more anterior (i.e., limited) it was in the P-LoS. Although the CoP path length in the QS was larger in the BSCP group, those in the A-LoS and P-LoS were larger in the control group. The BSCP group also showed that the more anterior the CoPy position or the longer the CoP path length in the QS, the more decreased the anteroposterior LoS range was. Therefore, assessing various standing postures, including QS and anteroposterior LoS, is important to manage balance impairments in individuals with BSCP.

Effects of balance training combined with Schroth therapy on adolescents with mild idiopathic scoliosis: A six-week randomized controlled trial.

BACKGROUND: Adolescent idiopathic scoliosis (AIS) has a great negative impact on the physical and mental health of patients; thus, a range of effective, timely interventions are urgently needed. Currently, there is a lack of evidence to illustrate the effect of balance training in patients with AIS, and the traditional AIS therapy often ignores the recovery in balance function of patients with AIS. OBJECTIVE: To investigate the effect of balance training combined with Schroth therapy among adolescent with mild idiopathic scoliosis. METHODS: 59 adolescents (aged 10 to 18, 35.59% male) with idiopathic scoliosis were selected and divided into an intervention group (n= 30) and a control group (n= 29). Participants in both groups received routine rehabilitation treatment based on Schroth therapy, and balance training was added in the intervention group. The duration of treatment for both groups was 6 weeks. The Trunk Rotation Angle (ATR), Cobb angle, Scoliosis Research Society 22 (SRS-22) scale and balance function of the two groups were evaluated at baseline and after the intervention. RESULTS: No significant difference of outcomes were observed between groups at baseline (P> 0.05). After 6 weeks of intervention, the ATR, Cobb angle, SRS-22 and balance function of the two groups improved significantly compared with those before treatment (P< 0.05), and the intervention group had a significant improvement than the control group (P< 0.05). CONCLUSION: Balance training combined with Schroth therapy for adolescents with mild idiopathic scoliosis can significantly improve ATR, Cobb angle and quality of life, as well as overall balance function.

Propagation of registration error into maximum total point motion to analyze tibial baseplate stability at six months using marker-based and model-based RSA.

Maximum total point motion (MTPM) of a tibial baseplate at 6 months is used to predict long-term aseptic loosening after total knee arthroplasty. However, the propagation of registration error into MTPM for stable baseplates (i.e. baseplates with MTPM < 0.5 mm) manifested as bias (i.e. systematic error) and precision (i.e. random error) has not been quantified and compared to the 6-month stability limit for marker-based and model-based RSA, which have different magnitudes of registration error. To determine the bias and precision in MTPM for stable baseplates, registration errors in six degrees of freedom reported in the literature for marker-based and model-based RSA were applied to an example baseplate using computer simulations. Results revealed that the bias in MTPM for stable baseplates with model-based RSA is three to four times that of marker-based RSA, and that the precision in MTPM for stable baseplates with model-based RSA is double that of marker-based RSA. This assessment of bias and precision in MTPM for stable baseplates led to a method for adjusting the 6-month stability limit for model-based RSA where half the width of the 95% confidence interval on the mean MTPM and the bias in MTPM for marker-based RSA were subtracted from 0.5 mm to compute true MTPM. The bias in MTPM and half the width of the 95% confidence interval on the mean MTPM for model-based RSA were then added to the true MTPM to obtain the adjusted stability limit for model-based RSA which ranged from 0.57 mm to 0.64 mm.

Does inspiration efficiency influence the stability limits of the trunk in patients with chronic low back pain?

OBJECTIVE: To determine the effects of diaphragm-strengthening training on the stability limits of the trunk and inspiratory function in patients with low back pain. DESIGN: A randomized comparative trial including a diaphragm training group that took part in conventional training together with diaphragm strengthening, and a control group that took part in conventional training only. Both groups participated in an 8-week training, 2 times/week. All subjects underwent the same measurement protocol before and after the intervention. PATIENTS: The study included 52 subjects with chronic low back pain. METHODS: The inspiratory functions (chest excursion, maximal inspiratory pressure, peak inspiratory flow, and volume of inspired air) and stability limits of the trunk with the subject in the sitting position (modified functional and lateral reach test) were assessed. RESULTS: Maximal inspiratory pressure and stability limit tests showed a statistically significant improvement only in the diaphragm training group. Statistically significant improvements in chest excursion and peak expiratory flow tests were found in both groups; however, the improvement was more greater in the diaphragm training group. CONCLUSION: Conventional exercises together with diaphragm training result in a greater improvement than conventional exercises alone in patients with chronic low back pain.

Forward functional stability indicator (FFSI) as a reliable measure of limits of stability.

Functional stability has been studied in diverse populations, yet the possibility to compare the results across them and the knowledge about actual performance referenced to the maximum capacity is limited. Our aim was to improve the functional limits of stability testing and introduced Forward Functional Stability Indicator (FFSI) as a reliable measure of functional stability. The study participants were not able to cross the projected forward anatomical stability limit (FASL). It is located at the level of first metatarsophalangeal joints and should be considered a mechanical limit of the maximal voluntary centre of foot pressure (COP) excursion (MVE). It was only true when the whole feet were in contact with the ground. There were statistically significant differences in limits of stability (LOS) test results in the conditions when the heels were raised and the toes muscles were contracted isometrically. The proposed forward functional stability indicator (FFSI) is a highly reliable measure of functional stability, which provides information about the actual performance with reference to maximum capacity and is easy to compare across normal and clinical populations. •The proposed forward functional stability indicator (FFSI) is a highly reliable measure of functional stability.•FFSI provides information about the actual performance with reference to maximum capacity and is easy to compare across normal and clinical populations.•The forward anatomical stability limit (FASL) is located at the level of first metatarsophalangeal joints and should be considered a mechanical limit of the maximal voluntary centre of pressure (COP) excursion when certain measurement criteria are met.

Postural stability limits in manifest and premanifest Huntington's disease under different sensory conditions.

Increasing evidence indicates that Huntington's disease (HD) produces postural control impairments even before the clinical diagnosis. It has been suggested that postural disorders of HD patients are explained by deficits in the processing and integration of sensory information, but this hypothesis has been under-explored. In the present study, we evaluated the amplitude of the center of pressure (COP) displacement during maximum leaning in four directions (forward, backward, rightward and leftward) and under three sensory conditions (eyes open, eyes closed and eyes closed standing on foam). We assessed the stability limits in 20 individuals with a positive HD genetic test (12 premanifests; eight manifests HD) and 15 healthy controls. The COP displacements were analyzed during the first and second phases of maintenance of the maximum leaning position. Manifest HD patients showed significantly greater COP ranges than healthy controls in both learning phases and all sensory conditions, but the greatest deterioration of their performance was found in the foam condition. In contrast, premanifest HD patients displayed larger COP ranges than controls only during the second phase of maximum learning, especially in the foam condition. Furthermore, both HD groups had significantly smaller limits of stability than healthy subjects during the second phase of maximum learning. However, their ability to maintain the maximum leaning position was degraded during both learning phases. Together, these findings demonstrate that HD reduces the limits of stability even before the clinical disease onset. Furthermore, our results indicate that dynamic postural tasks with high demand for sensorimotor integration and especially the use of proprioception are highly sensitive to early HD disease processes. This dynamic postural task may become a useful biomarker of HD progression.