Functional alignment in total knee arthroplasty best achieves balanced gaps and minimal bone resections: an analysis comparing mechanical, kinematic and functional alignment strategies.

PURPOSE: Key concepts in total knee arthroplasty include restoration of limb alignment and soft-tissue balance. Although differences in balance have been reported amongst mechanical alignment (MA), kinematic alignment (KA) and functional alignment (FA) techniques, it remains unclear whether there are differences in gap imbalance or resection thicknesses when comparing different constitutional alignment subgroups. METHODS: MA (measured resection technique), KA (matched resections technique) and FA (technique based on the restricted KA boundaries) were compared in 116 consecutive patients undergoing 137 robotic-assisted cruciate-retaining total knee arthroplasties. The primary outcome was the proportion of balanced gaps (differential laxities ≤ 2 mm) for extension, flexion, medial and lateral gap measurements. Manual pre-resection laxity measurements were obtained for MA and KA and manual post-resection measurements were obtained for FA in 10° and in 90° of knee flexion. Secondary outcomes were resection depths and implant alignment. All outcomes were analysed per constitutional coronal alignment and joint line obliquity subgroups. RESULTS: The proportions of balance in all four gap measurements were 54.7%, 66.4% and 96.5%, with MA, KA and FA, respectively. Across all constitutional alignment types, FA achieved the highest proportion of balance. MA resected the least amount of bone from the medial tibial plateau. KA had femoral components in most valgus and most internally rotated, tibial components in most varus and was the most bone-preserving for the posteromedial femoral condyle. FA had the most externally rotated femoral components and was most bone-preserving for the distal femoral resections. CONCLUSION: The study shows that implant alignment to the mechanical axis or joint line anatomy (equal resections) alone does not guarantee a balanced total knee arthroplasty. FA resulted in the highest proportion of balanced knees across all analysed subgroups. Future research will consider whether one alignment philosophy leads to superior outcomes for different constitutional alignment subgroups. LEVEL OF EVIDENCE: Level II.

The Addition of Suture Tape to the Hamstring Graft Construct Does Not Reduce Instrumented Knee Laxity Following ACL Reconstruction.

Purpose: To establish the effect of the addition of suture tape to the hamstring graft construct through measurement of instrumented sagittal plane knee laxity at 6 months after anterior cruciate ligament reconstruction (ACLR). Methods: A retrospective analysis was undertaken of a consecutive series of primary ACLR performed between May 2017 and June 2019. Patients with concomitant or historic contralateral knee injury were excluded. Suture tape was included in the graft construct from the midpoint of the study period (May 2018). Sagittal plane knee laxity was quantified using the KT2000 arthrometer at 6 postoperative months. Mean side-to-side differences in sagittal plane laxity between the operated and contralateral, uninjured knees were compared for grafts with and without suture tape. Additional outcomes included comparison between suture tape application techniques (graft reinforcement versus augmentation), comparison between suture tape with and without iliotibial band (ITB) tenodesis and documentation of complications necessitating further surgery. Results: A total of 169 patients were eligible for inclusion. Seventy-two grafts included suture tape and 84 patients underwent concomitant ITB tenodesis. There was no significant difference in mean laxity between grafts containing suture tape (mean difference: 1.2 mm, SD: 2.6 mm) and those without (mean difference: 1.3 mm, SD: 2.1 mm), P = .83 (CI -.92 to 1.13). Neither were there significant differences in laxity when using suture tape with concomitant ITB tenodesis (mean difference: 1.1 mm, SD: 2.1 mm), P = .75 (CI -.79 to 1.09), or when comparing techniques: graft reinforcement (mean difference .9 mm, SD 2.6 mm); graft augmentation (mean difference: 1.5 mm, SD: 2.5 mm) P = .52 (CI -2.29 to 1.16). There were no complications associated with suture tape. Conclusions: The addition of suture tape to an autologous hamstring graft construct did not reduce instrumented sagittal knee laxity in the first 6 months after ACL reconstruction. As such, the clinical relevance of its use remains unknown. Level of Evidence: Level III, retrospective cohort study.

The importance of joint line obliquity: a radiological analysis of restricted boundaries in normal knee phenotypes to inform surgical decision making in kinematically aligned total knee arthroplasty.

PURPOSE: Restricted kinematic alignment (rKA) in total knee arthroplasty (TKA) aims to restore native soft tissue laxities while limiting alignment extremes that risk prosthetic failure. However, there is no consensus where restricted boundaries (RB) should be set. This study aims to determine the proportion of limbs in which constitutional alignment and joint line obliquity (JLO) would be restored with various RB scenarios, to inform decision making in rKA TKA. METHODS: The mechanical hip-knee-ankle (mHKA) angle, arithmetic hip-knee-ankle (aHKA) angle, lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured on radiographs of 500 normal knees. Incrementally wider RBs were then applied. The proportion of limbs within each increment was determined when RBs were applied only to HKA, or to HKA, LDFA and MPTA together. In addition, the proportion of limbs within published adjusted mechanical alignment (aMA) and rKA protocols were determined, as well as those within one, two and three standard deviations of the means for HKA, LDFA and MPTA. RESULTS: When restrictions to mHKA alone were applied, 74.0% and 97.8% of knees were captured with boundaries of ± 3° and ± 6° respectively. However, when the same boundaries to HKA were also applied to MPTA and LDFA, 36.2% and 91.0% of knees were captured respectively, highlighting the limiting effect that JLO has on restoration of normal knee phenotypes. When comparing previously published boundaries, aMA of 0° ± 3° captured 36.2%; rKA of 0° ± 3 for HKA and 85° to 95° for LDFA/MPTA captured 67.8%; rKA of - 5° to 4° HKA and 86°-93° for LDFA/MPTA captured 63%; and rKA of - 6° to + 3° for HKA and 84°-93° for LDFA/MPTA captured 85.4%. CONCLUSION: The greatest proportions of normal knee phenotypes were captured with boundaries that were centred around population means for HKA and JLO. Further, these findings demonstrate that restricting the JLO has a significant limiting influence on restoration of normal knee phenotypes beyond that of restricting HKA alone. LEVEL OF EVIDENCE: III.

Tibiofemoral dynamic stressed gap laxities correlate with compartment load measurements in robotic arm-assisted total knee arthroplasty.

AIMS: It is unknown whether gap laxities measured in robotic arm-assisted total knee arthroplasty (TKA) correlate to load sensor measurements. The aim of this study was to determine whether symmetry of the maximum medial and lateral gaps in extension and flexion was predictive of knee balance in extension and flexion respectively using different maximum thresholds of intercompartmental load difference (ICLD) to define balance. METHODS: A prospective cohort study of 165 patients undergoing functionally-aligned TKA was performed (176 TKAs). With trial components in situ, medial and lateral extension and flexion gaps were measured using robotic navigation while applying valgus and varus forces. The ICLD between medial and lateral compartments was measured in extension and flexion with the load sensor. The null hypothesis was that stressed gap symmetry would not correlate directly with sensor-defined soft tissue balance. RESULTS: In TKAs with a stressed medial-lateral gap difference of ≤1 mm, 147 (89%) had an ICLD of ≤15 lb in extension, and 112 (84%) had an ICLD of ≤ 15 lb in flexion; 157 (95%) had an ICLD ≤ 30 lb in extension, and 126 (94%) had an ICLD ≤ 30 lb in flexion; and 165 (100%) had an ICLD ≤ 60 lb in extension, and 133 (99%) had an ICLD ≤ 60 lb in flexion. With a 0 mm difference between the medial and lateral stressed gaps, 103 (91%) of TKA had an ICLD ≤ 15 lb in extension, decreasing to 155 (88%) when the difference between the medial and lateral stressed extension gaps increased to ± 3 mm. In flexion, 47 (77%) had an ICLD ≤ 15 lb with a medial-lateral gap difference of 0 mm, increasing to 147 (84%) at ± 3 mm. CONCLUSION: This study found a strong relationship between intercompartmental loads and gap symmetry in extension and flexion measured with prostheses in situ. The results suggest that ICLD and medial-lateral gap difference provide similar assessment of soft-tissue balance in robotic arm-assisted TKA. Cite this article: Bone Jt Open 2021;2(11):974-980.

A Comparative Cohort Study of Lumbar Microdiscectomy in Obese and Nonobese Patients.

STUDY DESIGN: Prospective comparative cohort study. OBJECTIVE: Investigate whether there is a difference in postoperative pain reduction, complication rate, and other markers of operative difficulty in obese and nonobese patients undergoing elective lumbar microdiscectomy by a single spinal surgeon. SUMMARY OF BACKGROUND DATA: Lumbar radiculopathy is a debilitating condition that affects obese and nonobese patients. There is reluctance among some surgeons to perform lumbar microdiscectomy in the obese population. METHODS: Over 3 years a group of 34 obese patients were compared with 34 nonobese patients from the same period. Operative duration, blood loss, unintentional durotomies, infection rate, hospital stay, and pain reduction were compared. RESULTS: Reduction in total pain (control, -82%; obese, -71%) and radicular leg pain (control, -98%; obese, -97%) were similar. The risk of superficial infections was greater in the obese group, but there was no difference in rate of serious complication in our small series. Operative duration was much longer in the obese group (control, 28 min; obese, 70 min), as was total hospital stay. CONCLUSIONS: We found good postoperative pain relief in both groups. There was no difference in radicular leg pain between obese and nonobese patients but total pain due to lumbago was greater preoperatively and postoperatively in the obese group making their total pain greater. There was no evidence of higher serious complication rate that would preclude offering operative lumbar microdiscectomy to obese patients due to their obesity alone. However, operative duration was significantly longer in obese patients and should be considered accordingly.

An analysis of partial width flexor tendon graft preparation on porcine models: the optimal split?

Partial width tendon grafts are commonly used in upper limb reconstructive surgery. Different techniques are described to harvest the graft including a "cheese wire" technique to split the tendon along its fibres with a filament. However no study has looked at the best material for this purpose. Fresh flexor tendons from pigs' trotters were used to analyse the splitting qualities of 11 different suture materials. The qualities assessed were: whether the suture material was successful in splitting the tendon, the average force required to split the tendon and the resulting quality of the spilt tendon graft. Whilst wire sutures produced a high quality of graft, they were awkward to use as they necessitated handling with a holder due to the higher forces required to split the tendon. Fibrewire provided the best result with respect to graft quality and ease of method as it combined the cutting strength of wire with the handling characteristics of a braided suture.

Volumes, spatial extents and a probabilistic atlas of the human basal ganglia and thalamus.

The basal ganglia and thalamus are involved in processing all physiological behaviors and affected by many diseases. Accurate localization is a crucial issue in neuroimaging, particularly when working with groups of normalized images in a standard stereotaxic space. Here, manual delineation of the central structures (thalamus; nucleus caudatus and accumbens; putamen, pallidum, substantia nigra) was performed on 30 high resolution MRIs of healthy young adults (15 female, median age 31 years) in native space. Protocol inter-rater reliabilities were quantified as structure overlap (similarity indices, SIs). Structural volumes were calculated in native space, and after spatial normalization to stereotaxic space (MNI/ICBM152) and in relation to hemispheric volumes. Spatial extents relative to the anterior commissure (AC) were extracted. The 30 resulting atlases were then used to create probabilistic maps in stereotaxic space. Inter-rater SIs were high at 0.85-0.92 except for the nucleus accumbens. In native space, caudate, nucleus accumbens and putamen were significantly larger on the left, and the globus pallidus larger in males. After normalizing for brain volume, the nucleus accumbens, putamen and thalamus were larger on the left, with the gender difference in the globus pallidus still detectable. Some of these volume differences translated into significantly different distances from the AC. The probabilistic maps showed that overall the central structures' boundaries are relatively unchanged after spatial normalization. We present a comprehensive assessment of thalamic and basal ganglia volumetric and geometric data in both native and stereotaxic spaces. Probabilistic maps in MNI/ICBM152 space will allow accurate localization in group analyses.

Statistical neuroanatomy of the human inferior frontal gyrus and probabilistic atlas in a standard stereotaxic space.

We manually defined the inferior frontal gyrus (IFG) on high-resolution MRIs in native space in 30 healthy subjects (15 female, median age 31 years; 15 male, median age 30 years), resulting in 30 individual atlases. Using standard software (SPM99), these were spatially transformed to a widely used stereotaxic space (MNI/ICBM 152) to create probabilistic maps. In native space, the total IFG volume was on average 5%, and the gray matter (GM) portion 12% larger in women (not significant). Expressed as a percentage of ipsilateral frontal lobe volume (i.e., correcting for brain size), the IFG was an average of 20%, and the GM portion of the IFG 27%, larger in women (P < 0.005). Correcting for total lobar volume yielded the same result. No asymmetry was found in IFG volumes. There were significant positional differences between the right and left IFGs, with the right IFG being further lateral in both native and stereotaxic space. Variability was similar on the left and right, but more pronounced anteriorly and superiorly. We show differences in IFG volume, composition, and position between sexes and between hemispheres. Applications include probabilistic determination of location in group studies, automatic labeling of new scans, and detection of anatomical abnormalities in patients.

Three-dimensional maximum probability atlas of the human brain, with particular reference to the temporal lobe.

Probabilistic atlases of neuroanatomy are more representative of population anatomy than single brain atlases. They allow anatomical labeling of the results of group studies in stereotaxic space, automated anatomical labeling of individual brain imaging datasets, and the statistical assessment of normal ranges for structure volumes and extents. No such manually constructed atlas is currently available for the frequently studied group of young adults. We studied 20 normal subjects (10 women, median age 31 years) with high-resolution magnetic resonance imaging (MRI) scanning. Images were nonuniformity corrected and reoriented along both the anterior-posterior commissure (AC-PC) line horizontally and the midsagittal plane sagittally. Building on our previous work, we have expanded and refined existing algorithms for the subdivision of MRI datasets into anatomical structures. The resulting algorithm is presented in the Appendix. Forty-nine structures were interactively defined as three-dimensional volumes-of-interest (VOIs). The resulting 20 individual atlases were spatially transformed (normalized) into standard stereotaxic space, using SPM99 software and the MNI/ICBM 152 template. We evaluated volume data for all structures both in native space and after spatial normalization, and used the normalized superimposed atlases to create a maximum probability map in stereotaxic space, which retains quantitative information regarding inter-subject variability. Its potential applications range from the automatic labeling of new scans to the detection of anatomical abnormalities in patients. Further data can be extracted from the atlas for the detailed analysis of individual structures.