Deep Flexion Research Articles

Sex-Based Differences and Asymmetry in Hip Kinematics During Unilateral Extension From Deep Hip Flexion.

The purpose of this study was to identify side-to-side and sex-based differences in hip kinematics during a unilateral step-up from deep flexion. Twelve (eight men, four women) asymptomatic young adults performed a step ascent motion while synchronized biplane radiographs of the hip were collected at 50 images per second. Femur and pelvis position were determined using a validated volumetric model-based tracking technique that matched digitally reconstructed radiographs created from subject-specific computed tomography (CT) bone models to each pair of synchronized radiographs. Hip kinematics and side-to-side differences were calculated and a linear mixed effects model evaluated sex-based differences. Women were on average 10.2 deg more abducted and 0.2 mm more medially translated than men across the step up motion (p < 0.001). Asymmetry between hips was up to 14.1 ± 12.1 deg in internal rotation and 1.3 ± 1.4 mm in translation. This dataset demonstrates the inherent asymmetry during movements involving unilateral hip extension from deep flexion and may be used provide context for observed kinematics differences following surgery or rehabilitation. Previously reported kinematic differences between total hip arthroplasty and contralateral hips may be well within the natural side-to-side differences that exist in asymptomatic native hips.

Changes in the anteroposterior position of the femur relative to the tibia impact patient satisfaction in total knee arthroplasty

BackgroundIn this study, we aimed to investigate the preoperative and postoperative anteroposterior position (AP) of the femur relative to the tibia in total knee arthroplasty (TKA) and assess the influence of change in the AP position on clinical outcomes.MethodsWe evaluated 49 knees that underwent bi-cruciate-substituted TKA using a navigation system. The preoperative and postoperative AP position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60°, 90°, 105°, and 120° and maximum flexion angles were calculated. The 2011 Knee Society Score was evaluated preoperatively and 1 year postoperatively. The Wilcoxon signed rank and Spearman’s rank correlation tests were performed, with statistical significance set at P < 0.05.ResultsThe postoperative AP position was significantly correlated with the preoperative AP position at each measured angle. The postoperative AP positions were statistically more anterior than those preoperatively. Furthermore, the changes in the AP position after TKA negatively correlated with the symptom (P = 0.027 at 30°, P = 0.0018 at 45°, P = 0.0003 at 60°, P = 0.01 at 90°, and P = 0.028 at 105°) and patient satisfaction (P = 0.018 at 60° and P = 0.009 at 90°) scores at 1 year postoperatively.ConclusionThe postoperative AP position of the femur relative to the tibia was strongly influenced by the preoperative those in TKA. Postoperative anterior deviation of the femur relative to the tibia from mid-flexion to deep flexion could worsen clinical outcomes.

The Effect of Gracilis Tendon Preservation on Postoperative Knee Joint Stability and Muscle Strength in Arthroscopic Anterior Cruciate Ligament Reconstruction Surgery.

The aim of our study is to evaluate preserving gracilis tendon in anterior cruciate ligament reconstruction (ACLR) surgery and its effect to the flexion of the knee joint and tibial internal rotation strength and the stability of the knee. Patients who underwent primary single-bundle arthroscopic ACLR using all-inside technique and using hamstring tendon autograft were evaluated retrospectively. Patients were divided into two groups as gracilis preserved (St) and gracilis harvested (StG) groups. The International Knee Documentation Committee (IKDC) score, Lysholm, Knee Injury and Osteoarthritis Outcome Score-Knee-related quality of life (KOOS-QOL) score, ACL-Return to Sport after Injury scale score were used to evaluate as postoperative functional scores at last follow-up. Anterior tibial translation was evaluated using the KT-1000 device. Knee joint flexion, extension, and internal rotation strength were evaluated using isokinetic dynamometer. Dynamic balance performances were measured using the Biodex Balance System. There were 24 patients in the St group and 23 patients in the StG group. Demographic data and clinical results showed no significant difference. Anteroposterior movement of the tibia was found to be significantly higher in the StG group than in the St group in measurements at 89 and 134 N, respectively (p = 0.01 and <0.001). No statistically significant difference was found between both standard and deep flexor and extensor and internal rotator strength. No statistically significant difference was found in the amount of total, anteroposterior, and mediolateral balance deficit between the two groups. Additional gracilis harvesting does not have a negative effect on both standard and deep knee flexion, and tibial internal rotation strength compared with the St group. Although semitendinosus and StG group showed significantly more anterior tibial translation, there was no significant difference in clinical and dynamic stability measurements.

Propensity of the tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in Oxford unicompartmental knee arthroplasty: retrospective study.

A well-balanced joint gap is necessary in Oxford unicompartmental knee arthroplasty (OUKA) to prevent mobile-bearing dislocation. While the gaps between 20° (extension) and 100° (flexion) are precisely adjusted using the incremental mill system, there has been insufficient evaluation of gaps in other angles. We hypothesized that the gap is not always the same in other angles. This retrospective study aimed to evaluate the gap in full-extension (0°), mid-flexion (60°) and deep flexion (130°) for comparison with those in extension and flexion gaps. We evaluated 119 knees in 83 patients (51 females, 31 males, aged 71.9 years). The full-extension and mid-flexion gaps were compared with the extension gap, and the deep flexion gap was contrasted with the flexion gap. Each gap was classified into isometric, tight or loose, for evaluation of contributing factors. Although the full-extension gap tended to be isometric (45%), the mid-flexion tended to be tight (48%), whereas the deep-flexion was loose in most knees (84%) (P = 0.002). The tight mid-flexion and loose deep flexion gap pattern accounted for 44% of the total knees, especially so with smaller femoral components (P = 0.004). Our results highlight the propensity of tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in OUKA. Although the effect of such a minor gap imbalance is still unknown, the pattern was more prevalent in patients with smaller-sized femoral components. Use of a larger femoral component may equalize the gap throughout the motion arc.

MR imaging methods to study meniscal position and mechanics

ObjectiveMeniscal mechanics have been studied widely due to the high prevalence of meniscal injuries and their strong association with knee degeneration. Computational models and cadaver studies have contributed to our understanding of the menisci but require assumptions to extrapolate to living people. Imaging modalities provide the ability to make key measurements in vivo. In particular, magnetic resonance imaging (MRI) provides the three-dimensional (3D) visualization of the menisci required to make important measurements related to mechanical function. This mini review summarizes MR approaches that have been used to make measurements related to meniscal mechanics, including morphology, position, movement, shape, and extrusion. DesignA literature search was performed using PubMed and Google Scholar, with search terms including “meniscus” and “MRI” in combination with “mechanics”, “position”, “shape”, “movement”, “size”, “loaded”, and “unloaded”. Articles were manually reviewed and selected by consensus between the authors as constituting the most important examples of work required to illustrate the breadth of measurement and imaging approaches used in research on meniscal function. ResultsMRI has been used for quantitative 3D analyses of the morphology and position of the menisci. Morphological analyses included measurements of meniscal volume, thickness, width, and bulging. Positional analyses included measurements of the overlap between the meniscal surface and tibial joint surface, the amount of extrusion, and the percentage of joint surface area and meniscal area that were covered or uncovered. Open MR scanners have been used to measure the movement of the menisci from full extension to deep flexion. MR compatible loading devices have been used to study the effect of loading on meniscal morphology and extrusion. Studies using these methods have found that there are differences in meniscal morphology between healthy and osteoarthritic participants, that the lateral meniscus and anterior horns have greater movement throughout flexion, and that meniscal extrusion increases under load. ConclusionsMRI has improved our insight into meniscal mechanics. Simulated weightbearing, open imaging through the range of knee flexion, and image processing to yield 3D measurements have all contributed to this progress. These approaches have strong potential to explore clinically motivated research questions related to meniscal mechanics.

Snapping Biceps Femoris Repair: A Rare Cause of Lateral Knee Pain

Background: Snapping biceps femoris syndrome (SFS) represents a rare clinical entity in which the biceps femoris subluxates over the fibular head in deep flexion. Two primary pathophysiologies have been described including a prominent or abnormal fibular head morphology. Others have implicated an anomalous biceps femoris insertion. The diagnosis is made clinically, with operative and nonoperative intervention strategies available for treatment. Indications: SFS often results in audible snapping and associated pain at the lateral fibular head. When recalcitrant to nonoperative management, surgical intervention can lead to resolution of symptoms. We present the case of a college-aged male who has bilateral symptoms, worse on the right, which have resulted in significant activity modification and daily discomfort recalcitrant to anti-inflammatory medication and physical therapy. Technique Description: The patient was placed supine on the operating room table with an ipsilateral bump under the hip to assist in exposure of the lateral aspect of the knee. Examination under anesthesia (EUA) confirmed the snapping biceps femoris. A lateral approach to the knee and a common peroneal neurolysis was performed. The biceps femoris insertional anatomy was examined for anomalous tendon insertion or insertional tearing. The prominent fibular head was exposed and resected, with careful attention not to disrupt the lateral collateral ligament or popliteofibular ligament insertion sites. The biceps femoris was then repaired to the prepared bony bed of the fibula with one double-loaded suture anchor. Repeat EUA confirmed complete resolution of snapping even with maximal internal rotation of the tibia; this was carefully examined again with the tourniquet deflated to ensure its compressive effect was not partially responsible for the resolution. Results: Published data pertaining to SFS is limited to case reports and small case series. With appropriate indications, surgical intervention yields promising results with a high percentage of patients returning to prior level of activity or prior participation level in sport. Discussion/Conclusion: SFS can be diagnosed with a careful clinical assessment. When recalcitrant to nonoperative management, it is effectively treated with surgical intervention to restore normal fibular anatomy, and prevent recurrent instability and persistent pain. The presented technique allows for appropriate management of these rare injuries. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Muscle Morphology Does Not Solely Determine Knee Flexion Weakness After Anterior Cruciate Ligament Reconstruction with a Semitendinosus Tendon Graft: A Combined Experimental and Computational Modeling Study.

The distal semitendinosus tendon is commonly harvested for anterior cruciate ligament reconstruction, inducing substantial morbidity at the knee. The aim of this study was to probe how morphological changes of the semitendinosus muscle after harvest of its distal tendon for anterior cruciate ligament reconstruction affects knee flexion strength and whether the knee flexor synergists can compensate for the knee flexion weakness. Ten participants 8-18months after anterior cruciate ligament reconstruction with an ipsilateral distal semitendinosus tendon autograft performed isometric knee flexion strength testing (15°, 45°, 60°, and 90°; 0° = knee extension) positioned prone on an isokinetic dynamometer. Morphological parameters extracted from magnetic resonance images were used to inform a musculoskeletal model. Knee flexion moments estimated by the model were then compared with those measured experimentally at each knee angle position. A statistically significant between-leg difference in experimentally-measured maximal isometric strength was found at 60° and 90°, but not 15° or 45°, of knee flexion. The musculoskeletal model matched the between-leg differences observed in experimental knee flexion moments at 15° and 45° but did not well estimate between-leg differences with a more flexed knee, particularly at 90°. Further, the knee flexor synergists could not physiologically compensate for weakness in deep knee flexion. These results suggest additional factors other than knee flexor muscle morphology play a role in knee flexion weakness following anterior cruciate ligament reconstruction with a distal semitendinosus tendon graft and thus more work at neural and microscopic levels is required for informing treatment and rehabilitation in this demographic.

Insufficient stem antetorsion and lower cup abduction is a combined risk factor for posterior hip dislocation in patients undergoing THA for femoral neck fractures: a retrospective analysis

BackgroundThe role of acetabular and femoral component positions with respect to the risk of post-operative instability and dislocation remains debated. In this study, we aimed to identify potential risk factors for early dislocation following primary total hip arthroplasty (THA) for displaced intracapsular femoral neck fractures (FNF) using radiological measurements.MethodsWe retrospectively analyzed data for patients who underwent cementless primary THA for FNF using a posterolateral approach between January 2018 and December 2021. Follow-up duration, age, sex, affected side, and mean time from THA to dislocation were recorded. Leg-length inequality, abductor lever arm, vertical and horizontal femoral offsets, vertical and horizontal hip centers of rotation, abduction, anteversion of the acetabulum and femoral prosthesis, and combined anteversion were measured.ResultsThe study sample included 17 men and 34 women, with 21 and 30 patients undergoing left- and right-hip operations, respectively. The mean patient age was 70.18 ± 7.64 years, and the mean follow-up duration was 27.73 ± 13.52 months. The mean time between THA and dislocation was 1.58 ± 0.79 months. Seven patients (13.73%) sustained posterior dislocation of the hip. The abduction angle (36.05 ± 6.82° vs. 45.68 ± 8.78°) (p = 0.008) and anteversion of the femoral prosthesis (8.26 ± 4.47° vs. 19.47 ± 9.01°) (p = 0.002) were significantly lower in the dislocation group than in the control group. There were no significant differences in other parameters.ConclusionsInsufficient stem antetorsion combined with lower abduction angle of the acetabular component were associated with a high risk of dislocation, especially in patients with deep flexion or internal rotation of the flexed hip joint and knees, or in patients with a stiff spine or anterior pelvic tilt, impingement may then occur in the neck of the prosthesis and cup component, ultimately resulting in posterior dislocation. These findings could remind surgeons to avoid simultaneous occurrence of both in THA surgery. These results provide new insight into risk factors for hip dislocation in patients undergoing primary THA for FNF and may aid in reducing the risk of instability and dislocation.Level of evidenceProspective comparative study Level II.

Conservative Treatment Using Platelet-Rich Plasma for Acute Anterior Cruciate Ligament Injuries in Highly Active Patients: A Retrospective Survey.

Background The recommended treatment for anterior cruciate ligament (ACL) injuries in active, sports-oriented patients is reconstructive surgery in order to regain stability and prevent secondary meniscal injuries. However, ACL reconstruction requires a long recovery period and poses issues such as decreased muscle strength due to tendon harvesting and postoperative osteoarthritis (OA) progression, thereby raising significant expectations for the advancement of conservative treatments. Recent studies have shown that platelet-rich plasma (PRP) therapy, which utilizes the tissue repair-promoting property of platelets, is effective for ACL injuries. Methods We administered PRP therapy within six weeks after ACL injury in patients who expressed the desire for an early return to sports through conservative care. After the treatment, patients wore a simple brace that limited deep flexion but placed no restrictions on weight bearing. Four months was the standard goal established for returning to pre-injury condition, and, depending on the target level, timing, and knee condition, we adjusted the additional PRP treatments and rehabilitation approach, gradually authorizing the patients' return to sport. We assessed the ligament repair status by magnetic resonance imaging (MRI) just before the full return to sports.A retrospective survey was conducted to evaluate the status of ligament repair and the condition of return-to-sport in patients with ACLinjuries who underwent conservative treatment using PRP. Results The average patient age was 32.7 years and the average treatment was 2.8 PRP sessions. MRI evaluations confirmed that ligament continuity was regained in all cases. All the patients returned to their pre-injury level (Tegner Activity Scale 7.0) in an average of 139.5 days, but there was one instance of re-rupture following the return to sports. Conclusion All patients with ACL injury who underwent PRP therapy regained ligament continuity and returned to sport successfully with only one case of re-rupture.

Suprapatellar tibial fracture nailing is associated with lower rate for acute compartment syndrome and the need for fasciotomy compared with the infrapatellar approach

BackgroundIntramedullary tibial nailing (IMN) is the gold standard for stabilizing tibial shaft fractures. IMN can be performed through an infra- or suprapatellar approach.PurposeThe aim of this study is to compare the rate of fasciotomies for acute compartment syndrome between infra- and suprapatellar approaches.MethodsA total of 614 consecutive patients who were treated with IMN for tibial fracture between October 2007 and February 2020 were included in the study. The approach used for IMN was determined by the operating surgeon. Infrapatellar IMN was performed with the knee in deep flexion position, with or without calcaneal traction. Suprapatellar IMN was performed in straight or semiflexed position. The diagnosis of compartment syndrome was based on clinical analysis, but for some patients, a continuous compartment pressure measurement was used. The primary outcome was the rate of peri- and postoperative compartment syndrome treated with fasciotomies.ResultsThe study sample included 513 patients treated with infrapatellar IMN and 101 patients treated with suprapatellar IMN technique. The mean age of the patients was 44.7 years (infrapatellar technique) and 48.4 years (suprapatellar technique). High energy trauma was seen in 138 (27%) patients treated with infrapatellar technique and in 39 (39%) patients treated with suprapatellar technique. In the suprapatellar group (n = 101), there were no cases of peri- or postoperative compartment syndrome treated with fasciotomies. In the infrapatellar group (n = 513), the need for fasciotomies was stated in 67 patients, 31 patients (6.0%) perioperatively and in 36 patients (7.0%) postoperatively. The rate of fasciotomies (0/101 versus 67/513 cases) differed significantly (p < 0.001). There were no significant differences in the fracture morphology or patient demographics between the study groups.ConclusionsThe suprapatellar technique is recommended over the infrapatellar approach in the treatment of tibial shaft fractures. The rate of peri- and postoperative compartment syndrome and the need for fasciotomies was significantly lower with the suprapatellar technique. The major cause of increased rate of peri- or postoperative acute compartment syndrome with infrapatellar IMN technique is presumably associated with the positioning of the patient during the operation.Level of evidence3.

Reinsertion of Posterior Meniscal Root for Management of Hypermobile Lateral Meniscus: Description of a Surgical Technique

Lateral meniscus hypermobility is a special condition in which the posterior horn of the lateral meniscus exhibits excessive mobility. This condition can cause pain and locking in the knee, especially during kneeling, deep flexion, or squatting. In this article, we present a surgical technique for the reinsertion of the posterior root of the external meniscus in cases of hypermobility without detachment. The objective is to increase the tension of the meniscotibial and meniscal popliteal ligaments to achieve meniscal stability. The procedure involves suturing the meniscal root and fixation using a knotless implant through a transosseous tunnel. This technique has proven to be effective in stabilizing the lateral meniscus in patients with hypermobility.

Clinical Relevance of Posterior Osteophyte Formation in Ultra-congruent Total Knee Arthroplasty: Midterm Radiographic Rollback and Impingement Analysis.

Posterior femoral condylar osteophytes were frequently observed in patients with the ultra-congruent (UC) deep-dish design prosthesis. Therefore, the purpose of the present study was to verify the clinical relevance of osteophyte formation in the UC design. From March 2014 to February 2018, a comparative study was conducted on 96 knees using the UC design. They were divided into 2 groups (group 1: osteophyte +, group 2: osteophyte -). Intraoperative findings, indirect femoral rollback assessment using 30° flexion and active full flexion lateral radiographs, serial change of the osteophyte, and outcomes were compared. The mean follow-up period was 49.35 ± 3.47 months in group 1 and 47.52 ± 3.37 months in group 2. Posterior component coverage was significantly different between the groups: group 1 exhibited more underhang and group 2 exhibited more overhang (p = 0.022). On the indirect assessment of the femoral rollback, there was a statistically significant difference in deep flexion and change in distance (p < 0.001 and p < 0.001, respectively). There was no statistical difference between the 2 groups in the American Knee Society knee and function score, and group 2 showed significant improvement in pain compared to group 1 in Western Ontario and McMaster University Arthritis Index pain score (p = 0.029). Posterior condylar osteophyte formation was related to posterior impingement. It was more frequently observed in the underhang of the femoral component and insufficient femoral rollback. In addition, it changed with time and caused negative effects, including a gradual decrease in flexion and more pain.

Fourier Analysis of the Vertical Ground Reaction Force During Walking: Applications for Quantifying Differences in Gait Strategies.

Time series biomechanical data inform our understanding of normal gait mechanics and pathomechanics. This study examines the utility of different quantitative methods to distinguish vertical ground reaction forces (VGRFs) from experimentally distinct gait strategies. The goals of this study are to compare measures of VGRF data-using the shape factor method and a Fourier series-based analysis-to (1)describe how these methods reflect and distinguish gait patterns and (2)determine which Fourier series coefficients discriminate normal walking, with a relatively stiff-legged gait, from compliant walking, using deep knee flexion and limited vertical oscillation. This study includes a reanalysis of previously presented VGRF data. We applied the shape factor method and fit 3- to 8-term Fourier series to zero-padded VGRF data. We compared VGRF renderings using Euclidean L2 distances and correlations stratified by gait strategy. Euclidean L2 distances improved with additional harmonics, with limited improvement after the seventh term. Euclidean L2 distances were greater in shape factor versus Fourier series renderings. In the 8 harmonic model, amplitudes of 9 Fourier coefficients-which contribute to VGRF features including peak and local minimum amplitudes and limb loading rates-were different between normal and compliant walking. The results suggest that Fourier series-based methods distinguish between gait strategies.

Improvement of rotational arc during deep flexion range of a novel designed polyethylene insert for posterior-stabilised total knee arthroplasty

BackgroundOne of the remaining issues in total knee arthroplasty (TKA) is achieving sufficient rotational arc during deep flexion range of the knee for specific postures such as the ‘seiza’ or cross-legged sitting. This study aimed to evaluate whether there was a change in the actual in vivo rotational arc during deep flexion range before and after a design change of polyethylene (PE) inserts. MethodsIn 50 posterior-stabilised TKA cases, knee kinematics, including rotational movement, were measured intraoperatively using an image-free navigation system to compare a newly designed PE insert with reduced the posterior lip with a conventional PE insert. Femoral–tibial rotational angles at 30°, 45°, 60°, 90°, 120°, and 130° knee flexion were evaluated. Varus/valgus instability, knee range of motion, and femoral rollback were also measured. Obtained parameters were compared between new and conventional PE inserts. The independent factors associated with rotational arc during deep flexion range (120° and 130° knee flexion) were analysed using multivariate analysis. ResultsThe newly designed PE insert demonstrated a significant increase in the rotational arc at 120° (22.9 ± 8.7° vs. 30.1 ± 11.9°, P < 0.001) and 130° (24.3 ± 9.5° vs. 32.5 ± 12.4°, P < 0.001) knee flexion compared with that with the conventionally designed posterior-stabilised insert. Multivariate analysis demonstrated that using the newly designed PE insert was an independent predictor of improved rotational arc during deep flexion range: regression coefficient was 11.2 (95% confidence interval 7.1–15.3, P < 0.001). ConclusionThe design change, which reduced the posterior lip of the PE insert, contributed to improved rotational arc in 120° and 130° deep flexion ranges.

Preserved posterior cruciate ligament contributed to knee sagittal stability, but not to rollback and deep knee flexion in cruciate-retaining total knee arthroplasty with a cruciate-substituting insert

PurposeNo previous report has compared the differences in postoperative functional outcomes between posterior cruciate ligament (PCL)-retaining (CR-) and PCL-sacrificing (CS-) total knee arthroplasty (TKA) with detailed intraoperative consideration of joint gap and balance. The purpose of this study was to evaluate the in vivo function of preserved PCL in TKA by comparing postoperative functional outcomes between CR- and CS-TKA with a cruciate-substituting insert (CS-insert), considering intraoperative influence factors, such as the posterior tibial slope, posterior condylar offset, joint gap, joint balance, and joint laxity. MethodsA total of 55 knees in 38 patients (27 knees from 18 patients in the CR group, and 28 knees from 20 patients in the CS group) were analyzed. Fluoroscopic evaluation under anesthesia in sagittal laxity, rollback amount, and the maximum flexion angles were compared between the groups. ResultsThere were no significant differences in intraoperative or postoperative all measurement values between the two groups, but the sagittal laxity was significantly smaller in the CR group [5.4% ± 4.5% (2.4 ± 2.1 mm)] than in the CS group [9.0 ± 3.8% (4.0 ± 1.7 mm)] (P ​< 0.01). There were no significant differences in the amount of rollback and postoperative maximum knee flexion angle between the groups. ConclusionsPreserved PCL in TKA with a CS-insert contributed to knee sagittal stability, but not to rollback and deep knee flexion.

Evaluating computed bony range of motion (BROM) by registering in-vitro cadaver-based functional range of motion (FROM) to a hip motion simulation

BackgroundWhile modern hip replacement planning relies on hip motion simulation (HMS), it lacks the capability to include soft-tissues and ligaments restraints on computed bony range of motion (BROM), often leading to an overestimation of the in-vivo functional range of motion (FROM). Furthermore, there is a lack of literature on BROM assessment in relation to FROM. Therefore, the study aimed to assess computed BROM using in-vitro cadaver-derived FROM measurements, registered to a CT-based in-house HMS, and to further investigate the effect of functional and anatomical hip joint centres (FHJC and AHJC) on BROM. MethodSeven limiting and three non-limiting circumducted passive FROM of four cadaver hips were measured using optical coordinate measuring machine with reference spheres (RSs) affixed to the pelvis and the femur, following CT-scan of the specimen. The RSs’ centres were used to register the measured FROM in HMS, enabling its virtual recreation to compute corresponding BROM by detecting nearest bony impingement. FHJC, estimated from non-limiting FROM, was compared with AHJC to examine their positional differences and effect on BROM. ResultsDifferences in BROM and FROM were minimal in deep flexion (3.0° ± 4.1°) and maximum internal rotation (IR) at deep flexion (3.0° ± 2.9°), but substantially greater in extension (53.2° ± 9.5°). Bony impingement was observed during flexion, and IR at deep flexion for two hips. The average positional difference between FHJC and AHJC was 3.1 ± 1.2 mm, resulting in BROM differences of 1°–13° across four motions. ConclusionsThe study provided greater insight into the applicability and reliability of computed BROM in pre-surgical planning.

In Vivo Weight-Bearing Kinematics for Constrained Versus Traditional Bicruciate Stabilized Total Knee Arthroplasty Cohorts Compared to the Normal Knee

BackgroundConstrained inserts in total knee arthroplasty (TKA) may offer additional stability, but can this insert type allow unrestricted movements or will the extra conformity cause kinematic conflict with the cam-post mechanism in deeper flexion? The objective of this study was to evaluate the weight-bearing kinematics of both traditional and constrained bicruciate stabilized (BCS) TKA inserts to determine if the rollback induced by the cam-post mechanism will work in unison with the constrained polyethylene insert. MethodsThis study used previously published 3-dimensional model fitting techniques to compare weight-bearing flexion and femoro-tibial condylar motion patterns for 20 patients who had a traditional insert, 20 patients who had a constrained insert, and 10 previously published nonimplanted knees, all performing a deep knee bend activity while under fluoroscopic surveillance. ResultsThe results from this study indicate that subjects having a bicruciate stabilized TKA experienced similar postoperative kinematics for both constrained and unconstrained insert options, comparable to normal knees. ConclusionsSubjects in this study having either a constrained or traditional insert experienced progressive rollback of both condyles, with the lateral condyle rolling more posterior than the medial condyle, leading to axial rotation. Although less in magnitude, these results were comparable to the normal knee in pattern, indicating that kinematic conflict did not occur for subjects having a constrained insert.

Taux de survie à 20 ans d’une prothèse totale de genou postérostabilisée mono-opérateur dans une population asiatique

IntroductionAs life expectancy has improved, the potential number of revision candidates is also expected to increase among patients who have undergone a total knee arthroplasty (TKA). The longevity of modern posterior stabilized knee prostheses after 20 years of use has not been well documented, especially in Asian populations that require a deeper flexion range due to a floor-based lifestyle. Hypothesis(1) The implant longevity regarding mechanical failures such as aseptic loosening and polyethylene (PE) wear would vary over a longer follow-up depending on the age groups; and (2) there would be unique risk factors for revision surgery in an Asian TKA cohort. Material and methodsWe conducted this age-stratified survival analysis in a consecutive series of 368 NexGen Legacy Posterior Stabilized (LPS) TKAs performed by a single surgeon. These cases were divided into four age groups (< 60 years, early 1960s, late 1960s, and ≥ 70 years). The implant longevity against aseptic mechanical failures was calculated using the Kaplan-Meier method. The revision surgery risk was evaluated using postoperative factors including a deep flexion capability(> 135°), and postoperative mechanical alignments. ResultsOverall survivorship was significantly lower in the youngest groups than other groups (Log-rank test, p=0.001). The cumulative 20-year implant longevity was more than 95% in the two oldest groups, but less than 60% in the youngest group. It was notable that the post-TKA implant longevity was not apparent up to 10 years between the age groups (p=0.073∼0.458). Aseptic loosening was observed with an earlier onset (3.1 to 18.9 years) trend than PE wear (9.8∼17.9 years), with most cases arising in the youngest groups. Flexion limitation and varus alignment were significant risks to aseptic loosening and PE wear (Cox proportional hazard regression: p=0.001 and 0.045, respectively). DiscussionA younger age (< 60 years), inability of postoperative deep flexion, and varus alignment were significant risk factors for aseptic loosening and PE wear after modern PS design in this Asian cohort. The difference in postoperative longevity affected by these factors was not obvious during the first 10 years but emerged over a second decade. Level of proofIII; retrospective cohort study.

Knee flexor muscle fatigue during repeated Nordic hamstring exercise.

Nordic hamstring exercise is an effective method for preventing hamstring strain injury. In this study, we investigated the response of knee flexors regarding increased muscle force and fatigue when the Nordic hamstring exercise was performed repeatedly to further understand how it can prevent hamstring strain injury. The Nordic hamstring exercise was performed 10 times by 53 athletes; knee flexor peak tensile force and the respective flexion angle were compared at different phases during this sequence: phase 1, 1st Nordic hamstring exercise force; phase 2, mean value during the 2-4th repetitions; phase 3, mean value during the 5-7th repetitions; and phase 4, mean value during the 8-10th repetitions. We also divided the knee flexor peak force into deep and slight flexion zones and evaluated changes during different phases. Knee flexor peak force was most significant in phase 2 and decreased during subsequent phases. The knee angle at which peak force was exerted was greatest in phase 1 and decreased thereafter. When we compared the knee flexor peak force in different flexion angle zones, increased muscle force in the slight flexion zone was greater than increased muscle force in the deep flexion zone in phases 2 and 3. Enhancement of the knee flexor force, especially in the slight flexion zone occurs after only a few repetitions of the Nordic hamstring exercise.

The influence of patellar height on patellofemoral contact force during total knee arthroplasty

PurposeResidual anterior knee pain following total knee arthroplasty was reported to be related to high patellofemoral contact force. This study tried to show the relationship between patellar height and patellofemoral contact force in vivo, which has been demonstrated only in vitro thus far. MethodsFifty-five patients who had undergone a primary mobile-bearing posterior-stabilized total knee arthroplasty (28 cases using PFC Sigma and 27 cases using Attune) were included. After all the trial prostheses were placed, the patellar contact forces on the medial and lateral sides were measured using specially designed two uniaxial ultrathin force transducers at 0°–135° of knee flexion guided by the navigation system. Correlations between the pre-operative Insall-Salvati index and the medial or lateral patellar contact force in each flexion angle were analyzed using linear regression. Correlations between each patellar contact force and postoperative flexion angle were also assessed. ResultThere was a positive correlation between Insall-Salvati index and the lateral patellar contact force at 135° of flexion in all the patients, at 120° and 135° of flexion in patients with PFC Sigma and 135° of flexion in patients with Attune. The lateral patellar contact force at 120° and 135° of flexion in patients with PFC Sigma inversely correlated with postoperative flexion angle. ConclusionsPatients with patella alta tended to demonstrate high lateral patellar contact force in deep knee flexion after total knee arthroplasty, which can affect the post operative flexion angle and should be treated to prevent residual anterior knee pain.