Design and Verification of a Metaphyseal Filling Stem for Total Hip Arthroplasty Based on Novel Measurements of Proximal Femoral Anatomy.

Background: Cementless metaphyseal filling stems rely on fixation in the medial-to-lateral and anterior-to-posterior (AP) planes. The purpose of this preclinical study was to develop Insignia, a new metaphyseal filling system to match the anatomy of the proximal femur, and then compare it to clinically successful stems in multiple simulations. Methods: In this preclinical study, the geometry of the proximal femur in the AP plane among 1321 healthy subjects was evaluated using computed tomography. This data was then used to design insignia. Preclinical studies were performed to compare the broaching effort required to prepare a canal using this system, assess the reliability of seating heights for the stem, and compare in vitro micromotion testing of the stem under simulated stair climb activity. Results: The proximal femur decreased approximately 50% in the AP plane spanning 20 mm above the lesser trochanter to 30 mm below the lesser trochanter. Additional bench top testing was performed, and the new stem system was found to demonstrate significantly reduced broaching effort (average 6 vs 29 hits, P-value = .000), reliable seating heights on stem placement, and 70% less proximal micromotion on 10,000-cyclic testing (P < .05) compared to another clinically successful metaphyseal filling stem. Conclusions: The AP dimension of the proximal femur decreases nearly 50% throughout its length. Metaphyseal filling stems that match the AP anatomy of the proximal femur may require fewer hits during broaching, yield reproducible seating heights, and reduce micromotion on cyclic testing.

Adolescents and adults with patellofemoral pain exhibit distinct patellar maltracking patterns.

BACKGROUND: Chronic idiopathic patellofemoral pain is associated with patellar maltracking in both adolescents and adults. To accurately target the underlying, patient-specific etiology, it is crucial we understand if age-of-pain-onset influences maltracking. METHODS: Twenty adolescents (13.9 ± 1.4 years) and 20 adults (28.1 ± 4.9 years) female patients with idiopathic patellofemoral pain (age-of-pain-onset: < 14 and > 18 years of age, respectively) formed the patient cohort. Twenty adolescents and 20 adults (matched for gender, age, and body mass index) formed the control cohort. We captured three-dimensional patellofemoral kinematics during knee flexion-extension using dynamic MRI. Patellar maltracking (deviation in patient-specific patellofemoral kinematics, relative to their respective age-controlled mean values) was the primary outcome measure, which was compared between individuals with adolescent-onset and adult-onset patellofemoral pain using ANOVA and discriminant analysis. FINDINGS: The female adolescent-onset patellofemoral pain cohort demonstrated increased lateral (P = 0.032), superior (P = 0.007), and posterior (P < 0.001) maltracking, with increased patellar flexion (P < 0.001) and medial spin (P = 0.002), relative to the adult-onset patellofemoral pain cohort. Post-hoc analyses revealed increased lateral shift [mean difference ± 95% confidence interval = -2.9 ± 2.1 mm at 10° knee angle], posterior shift [-2.8 ± 2.1 mm, -3.3 ± 2.3 mm & -3.1 ± 2.4 mm at 10°, 20°& 30°], with greater patellar flexion [3.8 ± 2.6 mm & 5.0 ± 2.8 mm, at 20°& 30°] and medial spin [-2.2 ± 1.7 mm & -3.4 ± 2.3 mm at 20°& 30°]. Axial-plane maltracking accurately differentiated the patient age-of-pain-onset (60-75%, P < 0.001). INTERPRETATION: Age-of-pain-onset influences the maltracking patterns seen in patients with patellofemoral pain; with all, but 1, degree of freedom being unique in the adolescent-onset-patellofemoral pain cohort. Clinical awareness of this distinction is crucial for correctly diagnosing a patient's pain etiology and optimizing interventional strategies.

Perioperative Continuation of Biologic Medications Increases Odds of Periprosthetic Joint Infection in Patients With Inflammatory Arthropathy.

BACKGROUND: Rates of prosthetic joint infection (PJI) are elevated among patients with inflammatory arthropathy (IA). The effect of continuing biologic drugs perioperatively with regard to PJI is unknown. The purpose of this study is to compare rates of perioperative biologic continuation in IA patients who did and did not develop PJI after primary total joint arthroplasty (TJA). METHODS: All cases of PJI within 1 year of primary TJA in IA patients on biologic medications were retrospectively reviewed from 2005 to 2018 in the US Veterans Affairs Corporate Data Warehouse. Matched controls who did not develop PJI after TJA were populated from the same database. Biologic suspension, defined as medication interruption prior to TJA with surgery occurring after the end of the dosing cycle and resumption after wound healing, was compared among cases and controls. RESULTS: Biologic medications were continued through surgery in 35% (9/26) of patients who developed PJI compared to 14% (8/58) of controls (P = .031; adjusted odds ratio of 3.46 [1.11-10.78]). No significant difference existed among cases (n = 26) and controls (n = 58) for age, gender, procedure, body mass index, rates of diabetes or chronic kidney disease, smoking status, or preoperative opioid use (all P > .05). CONCLUSION: With the limited sample sizes available in this study, we found an association with perioperative continuation of biologic medications and PJI. This data may provide support for current guidelines from the American Association of Hip and Knee Surgeons to withhold biologics before TJA with surgery scheduled at the end of the dosing cycle and medication resumption only after wound healing.

High Rates of Spacer Fracture in the Setting of Extended Trochanteric Osteotomy With a Specific Thin-Core Articulating Antibiotic Hip Spacer.

BACKGROUND: Two-stage revision remains the standard of care for prosthetic joint infection after total hip arthroplasty. However, there are substantial complications associated with articulating antibiotic hip spacers. Handmade and molded spacers have been shown to have higher rates of spacer fracture than antibiotic-coated prostheses (ACPs). The aim of this study is to review outcomes with an implant that is often categorized as an ACP spacer, the Zimmer-Biomet StageOne Select Femoral Spacer (ZBSO). METHODS: A retrospective review was performed of 63 patients who underwent placement of a ZBSO. Patients were compared based on whether or not an extended trochanteric osteotomy (ETO) was performed using Fisher's exact and t-tests. RESULTS: Five patients were excluded due to lack of follow-up or death shortly after stage 1 surgery, leaving 58 patients. Spacer fracture was noted in 5 of 58 patients (8.6%). Sixteen patients underwent ETO and 25.0% suffered a spacer fracture compared to 2.3% without ETO (odds ratio 13.7, P = .0248). There was no association between patient demographics or ETO length and spacer fracture. Two patients had periprosthetic fractures (3.4%) and 4 had dislocations (6.9%). Forty-nine patients (84.4%) went on to second-stage revision; of those 26.5% failed to clear the infection and required an average of 2.2 additional surgeries. CONCLUSION: The ZBSO spacer has overall complication rates similar to previously reported spacer series. Although the ZBSO looks like an ACP spacer, in the setting of ETO, it behaves like a molded or handmade spacer with a high rate of spacer fracture (25%) due to the small diameter of the core. This implant should be used with caution in combination with an ETO.

Are We Being Fooled by Fluoroscopy? Distortion May Affect Limb-Length Measurements in Direct Anterior Total Hip Arthroplasty.

BACKGROUND: Distortion is an intrinsic phenomenon associated with image-intensified fluoroscopy that is both poorly understood and infrequently appreciated by orthopedic surgeons. Little information exists regarding its potential influence on intraoperative parameters during orthopedic surgery, let alone during direct anterior (DA) total hip arthroplasty (THA). The purpose of this study was to quantify the amount of potential error caused by fluoroscopic distortion during DA THA. METHODS: Intra-operative fluoroscopic pelvic images from 74 DA THAs were reviewed by two independent readers. All images were obtained using the same fluoroscopic C-arm unit with a radiopaque grid attached to the image intensifier. The vertical distortion from a straight central horizontal line at the peripheries of images were measured and summed to yield the combined vertical distortion similar to how a surgeon calculates a side to side comparison of limb lengths. Simple linear regression was used to evaluate associations between total distortion and patient demographics, operating theaters, and various operative parameters. RESULTS: The average combined distortion was 10.0mm (range 2.0-20.0mm). There was a significant difference in the average distortion observed in different theaters (P < .001). There was no association between distortion and patient demographics or fluoroscopic time (all, P > .05). CONCLUSION: Fluoroscopic distortion is unpredictable and can cause a substantial amount of error when comparing limb lengths during DA THA. This is a critical finding as this amount of inaccuracy could lead to unintended implant positioning and limb-length discrepancies if unaccounted for.

Clinical Experience With a Coordinated Multidisciplinary Approach to Treating Prosthetic Joint Infection.

The successful treatment of prosthetic joint infection (PJI) is difficult, requiring coordination across multiple specialties. In 2017, we formed a collaboration between our infectious disease clinicians and our orthopaedic arthroplasty surgeons in an effort to optimize care, accommodate patients, and expedite clinical decision-making in the treatment of PJI. The model consisted of combined infectious disease and arthroplasty clinics, standardized lab results, and planned staged revision procedures. We named this the arthroplasty infection service. Our early experience with a defined multidisciplinary approach to PJI was positive. Although the impact of the arthroplasty infection service on PJI outcomes is yet to be determined, we believe this is a step forward in the management of this complex patient population. With an increasing burden of PJI in the United States, this model could be emulated at many institutions that regularly treat these challenging cases.

Balanced, Stemmed, and Augmented Articulating Total Knee Spacer Technique.

Explantation and placement of an antibiotic spacer is a well-recognized treatment for periprosthetic infection after total knee replacement. Although static spacers may be occasionally indicated, many patients benefit from an articulating spacer that preserves the function and range of motion. However, many articulating spacer techniques provide an imbalanced cement-on-cement articulating knee that cannot tolerate full weight-bearing or provide adequate stability for daily function. A more durable articulating spacer may be ideal by permitting unrestricted weight-bearing, a functional range of motion, and potentially delayed reimplantation for medically complex patients. We present our evolved and reproducible technique for gap-balanced articulating spacers using cement augments and dowel stems. The result is a stable construct that permits full weight-bearing and a functional range of motion.

When Does the Knee Feel Normal Again: A Cross-Sectional Study Assessing the Forgotten Joint Score in Patients After Total Knee Arthroplasty.

BACKGROUND: The forgotten joint score (FJS) is a recent scoring system that assesses how natural the prosthesis feels after total joint arthroplasty. Although the FJS has been extensively applied in populations with total hip prosthetics, less is known about the patients undergoing total knee arthroplasty (TKA). The purpose of this study is to investigate the temporal relationship between TKA and the FJS. METHODS: We evaluated 566 patients after TKA using the FJS questionnaire. Scores were calculated at the follow-up intervals of 1 (n = 79), 6 (n = 78), 12 (n = 81), 24 (n = 100), 36 (n = 76), 48 (n = 75), and 60 (n = 77) months. The scores ranged from 0-100, with a higher score indicating a more natural or "forgotten" joint. RESULTS: Postoperative FJS averages were 39.3 ± 27.4 at 1 month, 59.4 ± 28.3 at 6 months, 72.5 ± 24.2 at 1 year, 76.4 ± 23.4 at 2 years, 75.1 ± 24.2 at 3 years, 68.6 ± 28.7 at 4 years, and 64.4 ± 29.0 at 5 years. The average score at 1 month was significantly lower than the average scores at all other intervals. The average score at 6 months was significantly lower than the average scores at 12, 24, and 36 months. The average score at 60 months was significantly lower than the average score at 24 months. CONCLUSION: Based on the findings of this study, patients can expect marked improvement in the natural feel of the prosthesis during the first year after TKA, slight continued improvement at 2 and 3 years, and a decline after 4 years.

The Direct Anterior Approach Does Not Increase Return to Function Following Hemiarthroplasty for Femoral Neck Fracture.

The purpose of this study was to evaluate functional outcomes for hemiarthroplasty using a direct anterior approach or a direct lateral approach for femoral neck fracture. This retrospective review used data collected from a single institution between 2006 and 2016. Eighty-five and 75 consecutive patients who underwent hemiarthroplasty via a direct anterior approach and a direct lateral approach, respectively, met inclusion criteria. All patients with femoral neck fractures were treated by 1 of 2 fellowship-trained orthopedic surgeons using the direct anterior approach or the direct lateral approach to hemiarthroplasty. Disposition, ambulation, and other perioperative surgical outcomes were compared between the cohorts. Compared with the direct lateral cohort, the direct anterior cohort had a shorter mean operative time (2.4 minutes, P<.01), a shorter mean length of hospital stay (2.7 days, P<.01), and a smaller mean decrease in hemoglobin postoperatively (0.7 g/dL, P<.01). No significant difference was observed between the cohorts for postoperative disposition, the number of feet ambulated on the second postoperative day, or the prevalence of ambulatory decline at 4- to 6-week and 4- to 6-month follow-up visits. Compared with the direct lateral approach, the direct anterior approach may benefit patients by small, but statistically significant, improvements in blood loss, surgical time, and length of hospital stay after hemiarthroplasty. However, the direct anterior approach does not appear to decrease the likelihood of transfer to a skilled nursing facility postoperatively or accelerate return to preoperative function. [Orthopedics. 2017; 40(6):e1055-e1061.].

The Relationship of Static Tibial Tubercle-Trochlear Groove Measurement and Dynamic Patellar Tracking.

BACKGROUND: The tibial tubercle to trochlear groove (TT-TG) distance is used for screening patients with a variety of patellofemoral joint disorders to determine who may benefit from patellar medialization using a tibial tubercle osteotomy. Clinically, the TT-TG distance is predominately based on static imaging with the knee in full extension; however, the predictive ability of this measure for dynamic patellar tracking patterns is unknown. PURPOSE: To determine whether the static TT-TG distance can predict dynamic lateral displacement of the patella. STUDY DESIGN: Cohort study (Diagnosis); Level of evidence, 2. METHODS: The static TT-TG distance was measured at full extension for 70 skeletally mature subjects with (n = 32) and without (n = 38) patellofemoral pain. The dynamic patellar tracking patterns were assessed from approximately 45° to 0° of knee flexion by use of dynamic cine-phase contrast magnetic resonance imaging. For each subject, the value of dynamic lateral tracking corresponding to the exact knee angle measured in the static images for that subject was identified. Linear regression analysis determined the predictive ability of static TT-TG distance for dynamic patellar lateral displacement for each cohort. RESULTS: The static TT-TG distance measured with the knee in full extension cannot accurately predict dynamic lateral displacement of the patella. There was weak predictive ability among subjects with patellofemoral pain ( r2 = 0.18, P = .02) and no predictive capability among controls. Among subjects with patellofemoral pain and static TT-TG distances 15 mm or more, 8 of 13 subjects (62%) demonstrated neutral or medial patellar tracking patterns. CONCLUSION: The static TT-TG distance cannot accurately predict dynamic lateral displacement of the patella. A large percentage of patients with patellofemoral pain and pathologically large TT-TG distances may have neutral to medial maltracking patterns.

Patellar Maltracking Persists in Adolescent Females With Patellofemoral Pain: A Longitudinal Study.

BACKGROUND: Patellofemoral pain is one of the most common conditions seen in sports medicine practices, particularly among adolescent females. However, the natural history of the underlying pathology in patellofemoral pain during puberty remains poorly understood. PURPOSE: The purpose of this longitudinal study is to assess changes in patellar maltracking patterns in subjects with patellofemoral pain as they mature from mid- to late adolescence. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Three-dimensional patellofemoral kinematic data were acquired during active knee extension-flexion using dynamic magnetic resonance imaging in 6 girls (10 knees; mean age, 14.0 years) with clinically diagnosed patellofemoral pain. The subjects then returned as late adolescents (mean age, 18.5 years) for follow-up scanning. Three-dimensional patellofemoral kinematic parameters were evaluated across the range of motion, but comparison between time points was restricted to 10° of flexion. Participation in impact and nonimpact physical activities, pain score based on the visual analog scale, and the anterior knee pain score were also compared across initial and follow-up visits. RESULTS: All subjects reported improved patellofemoral pain symptoms at follow-up, and one subject reported complete resolution. However, relative to the initial visit, no differences were found in patellar maltracking. There was a decrease in hours engaged in impact physical activities for all subjects at follow-up. CONCLUSION: This study provides insight into the natural history of patellofemoral pain in adolescent females. The relatively unchanged patellofemoral maltracking across subjects suggests that potential anatomic and kinematic abnormalities contributing to patellofemoral pain during mid-adolescence persist during skeletal maturation. Symptom improvement for these subjects did not result from a change in patellofemoral tracking, but rather from other causes.

The Tibial Tubercle-Trochlear Groove Distance Is Greater in Patients With Patellofemoral Pain: Implications for the Origin of Pain and Clinical Interventions.

BACKGROUND: The distance between the tibial tubercle (TT) and trochlear groove (TT-TG distance) is known to be greater in patients with patellar instability. However, the potential role and prevalence of pathological TT-TG distances in a large cohort of skeletally mature patients with isolated patellofemoral pain (PFP) are not clear. PURPOSE: To determine if the mean TT-TG distance is greater in patients with PFP, who lack a history of patellar dislocations, knee trauma, or osteoarthritis, relative to healthy controls. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 50 knees (38 patients) with PFP and 60 knees (56 controls) without PFP formed the basis of this study. Magnetic resonance imaging was used to determine the TT-TG distance from 3-dimensional static scans. RESULTS: The cohort with PFP demonstrated a significantly greater mean TT-TG distance relative to asymptomatic controls (13.0 vs 10.8 mm, respectively; P = .001). Among the cohort with PFP, 15 knees (30%) demonstrated TT-TG distances ≥15 mm, and 3 knees (6%) demonstrated TT-TG distances ≥20 mm. CONCLUSION: Most adult patients with isolated PFP have elevated TT-TG distances compared with controls, which likely contributes to the force imbalance surrounding the knee.

Patellofemoral Kinematics and Tibial Tuberosity-Trochlear Groove Distances in Female Adolescents With Patellofemoral Pain.

BACKGROUND: Patellofemoral pain (PFP) is a prevalent disorder among female adolescents. Overuse is frequently cited as the cause of pain for this population. What is currently unclear, however, is if the patella demonstrates abnormal tracking patterns relative to the femoral trochlear groove in female adolescents with PFP. PURPOSE: The aim of this case-control study was to determine if abnormal patellar tracking patterns are present in female adolescents with PFP. The secondary aim was to identify if an increased tibial tuberosity-trochlear groove (TT-TG) distance is associated with the observed kinematic patterns. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty female adolescent knees from 12 patients with PFP and 20 age-matched female knees from 13 healthy controls were recruited for this study. Patellofemoral kinematics (eg, lateral patellar displacement) during a repetitive knee extension-flexion maneuver was quantified by dynamic cine phase-contrast magnetic resonance imaging (MRI). Static MRI scans were used to determine the TT-TG distance. RESULTS: Relative to the control cohort, female adolescents with PFP demonstrated significantly greater lateral displacement at 10° (3.2 mm; P < .001), 20° (2.3 mm; P < .001), and 30° (1.7 mm; P = .014) of knee flexion. A subgroup within this cohort (7 knees from 5 patients) demonstrated extreme lateral maltracking >2 SDs of the mean of the control cohort. This subgroup also demonstrated a greater TT-TG distance relative to the controls (Δ = 4.2 mm; P = .001). CONCLUSION: This study demonstrates abnormal lateral patellar displacement in the absence of patellar tilt in female adolescents with PFP. Because all adolescents from both cohorts participated in impact sports, it appears that rigorous athletic training alone is inadequate to produce symptoms in this population. Rather, PFP may derive from a combination of physical activity in the context of pathological kinematics. CLINICAL RELEVANCE: Abnormal patellar tracking patterns and abnormal static alignment have been shown to contribute to the etiology of patellofemoral pain in adults. This study demonstrates that pathologic patellar tracking patterns are present in adolescent females with patellofemoral pain.

Video Analysis of Anterior Cruciate Ligament (ACL) Injuries: A Systematic Review.

BACKGROUND: As the most viable method for investigating in vivo anterior cruciate ligament (ACL) rupture, video analysis is critical for understanding ACL injury mechanisms and advancing preventative training programs. Despite the limited number of published studies involving video analysis, much has been gained through evaluating actual injury scenarios. METHODS: Studies meeting criteria for this systematic review were collected by performing a broad search of the ACL literature with use of variations and combinations of video recordings and ACL injuries. Both descriptive and analytical studies were included. RESULTS: Descriptive studies have identified specific conditions that increase the likelihood of an ACL injury. These conditions include close proximity to opposing players or other perturbations, high shoe-surface friction, and landing on the heel or the flat portion of the foot. Analytical studies have identified high-risk joint angles on landing, such as a combination of decreased ankle plantar flexion, decreased knee flexion, and increased hip flexion. CONCLUSIONS: The high-risk landing position appears to influence the likelihood of ACL injury to a much greater extent than inherent risk factors. As such, on the basis of the results of video analysis, preventative training should be applied broadly. Kinematic data from video analysis have provided insights into the dominant forces that are responsible for the injury (i.e., axial compression with potential contributions from quadriceps contraction and valgus loading). With the advances in video technology currently underway, video analysis will likely lead to enhanced understanding of non-contact ACL injury.