Towards a stabilized Kerr optical frequency comb with spatial interference.

We measured a soliton's carrier frequency created by a silicon nitride Kerr comb from an interference pattern created by a spatial interferometer. The optical frequencies were determined from the interference pattern by simultaneously calibrating against an interference pattern from the pump optical frequency. Results were compared to real-time measurements by an optical spectrum analyzer (OSA). The spatial interferometer and the OSA results tracked each other, and the resulting RMS error is presented.

Entrance pupil masks for enhancing moiré-based distance/motion sensing.

Detection of higher-order diffraction patterns when range-finding using moiré images of fork gratings, as previously developed, is key for increased sensitivity. However, higher-order frequencies are inherently lower contrast than the fundamental frequency. Here we explore means of optically increasing contrast of moiré patterns via pupil function design. Two candidate pupil forms that increase performance above diffraction limited capabilities at specific spatial frequencies are considered, and one is chosen to proceed to experimentation. Contrast of the moiré image when using the specially designed pupil is compared to a clear aperture. Both simulation and experimental data are analyzed to show the increased contrast and sensing capabilities of the candidate entrance pupil mask.

Entrapment of the Extensor Indicis Proprius Tendon after Open Reduction and Internal Fixation of Distal Ulna: Case Report and Discussion of the Diagnosis and Surgical Result.

Entrapment of the extensor indicis proprius (EIP) after open reduction and internal fixation (ORIF) of the distal ulna with a plate and screw construct is rare. By literature review, we found evidence of such complication associated with distal radius fracture, but no past reports relating to the distal ulna. ORIF of the distal ulna is a common procedure for both fracture treatment and deformity correction. Due to the EIP muscle originating primarily from the dorsoradial surface of the distal ulna and the adjacent interosseous membrane, the muscle may be damaged or compressed by a fixation plate during ORIF, resulting in entrapment. We present two case reports of this rare complication, describing the method of clinical diagnosis, surgical treatment, and outcome. Our accompanying cadaver dissection provides an explanation for proper plate positioning during ORIF of the ulna to reduce the risk of EIP entrapment.

Passive range finder based on moiré images of Ronchi-like gratings with bilateral asymmetry.

A passive range-finding technique utilizing moiré images of Ronchi-like gratings with bilateral asymmetry, specifically fork gratings, is explored. Fork gratings are used as opposed to Ronchi gratings due to their asymmetry in the spatial and frequency domains, which enable the resolution of certain ambiguities in analysis that would otherwise be present. The two patterns which are convolved to produce the moiré image are the fork grating and the nailbed pattern of the pixelated detector. A fork grating of known size and spatial frequency is imaged with a detector of a fixed pixel pitch. Multiple analysis techniques are applied in frequency space, which lead to both relative and absolute measures of distance.

Revision Multiligament Knee Reconstruction: Clinical Outcomes and Proposed Treatment Algorithm.

PURPOSE: To (1) assess clinical outcomes of revision multiligament knee injury (MLKI) reconstruction at a minimum of 2 years' follow-up and (2) present a standardized treatment algorithm used in treating revision MLKI patients. METHODS: A retrospective review of our institution's MLKI database was performed to identify all patients who underwent revision MLKI reconstructions (≥2 ligaments reconstructed) after implementation of a standardized treatment algorithm in 2000 and had a minimum of 2 years' follow-up. Patient demographic information, injury description (mechanism of injury, neurovascular status, knee dislocation grade, associated chondral or meniscal injury), surgical technique (repair vs reconstruction, staged vs nonstaged, concomitant procedures), mechanism of failure, knee stability, and range of motion, as well as International Knee Documentation Committee and Lysholm scores, were obtained. RESULTS: We assessed 23 patients (8 female and 15 male patients), with an average age of 26.7 ± 11.5 years at primary surgery and 30.8 ± 11.0 years at revision surgery. The mean follow-up period was 7.5 ± 5.3 years. Of the 23 patients, 10 (43.4%) underwent staged revision procedures: isolated bone grafting in 3, osteotomy in 4, hardware removal with osteochondral allograft in 1, hardware removal with bone grafting in 1, and meniscus repair for a locked knee in 1. The average International Knee Documentation Committee and Lysholm scores were 74.5 ± 22.3 and 79.4 ± 20.2, respectively. High-energy injury and increasing age at revision surgery were the only risk factors found to be associated with significantly worse outcomes (P < .05). CONCLUSIONS: Patients with recurrent instability after MLKI reconstruction present with many concomitant pathologies, including limb malalignment, bone tunnel widening, retained hardware, meniscal incompetence, and cartilage defects. Revision MLKI reconstruction can provide these patients with modest functional outcomes when a standardized treatment algorithm is used focusing on identification and treatment of the concomitant pathology, often in a staged manner. LEVEL OF EVIDENCE: Level IV, case series.

Non-operative management of medial meniscus posterior horn root tears is associated with worsening arthritis and poor clinical outcome at 5-year follow-up.

PURPOSE: Medial meniscus posterior root tears (MMPRTs) are a significant source of pain and dysfunction, but little is known about the natural history and outcome and for non-operative management of these lesions. The purpose of this study was to evaluate (1) the mid-term clinical and radiographic outcomes of non-operative treatment of MMPRTs and (2) risk factors for worse outcomes. METHODS: A retrospective review was performed for patients with symptomatic, unrepaired MMPRTs and a minimum 2-year follow-up for IKDC and Tegner outcome scores. Baseline and final radiographs were reviewed and graded according to Kellgren-Lawrence scores. Baseline MRIs were reviewed for the presence of meniscal extrusion, subchondral oedema, and insufficiency fractures. Failure was defined as conversion to arthroplasty or severely abnormal patient subjective IKDC score. RESULTS: Fifty-two patients (21M:31F) with a mean age of 58 ± 10 years were diagnosed with symptomatic MMPRTs clinically and confirmed by MRI and followed for a mean of 62 ± 30 months. Sixteen patients (31 %) underwent total knee arthroplasty at a mean of 30 ± 32 months after diagnosis with higher Kellgren-Lawrence grades associated with increased rates of arthroplasty (p = 0.01). Mean IKDC scores for the remaining patients were 61.2 ± 21 with significantly lower scores in females compared to males (75 ± 12 vs. 49 ± 20; p = 0.03). Mean Kellgren-Lawrence grades and rates of arthritis progressed over time on radiographs (1.5 ± 0.7 vs. 2.4 ± 1.0; p < 0.001 and 78 % vs. 51 %; p = 0.01). Overall, 87 % of patients failed non-operative treatment. CONCLUSIONS: Non-operative treatment of medial meniscus posterior horn root tears is associated with poor clinical outcome, worsening arthritis, and a relatively high rate of arthroplasty at 5-year follow-up. Female gender was associated with lower subjective scores and higher rate of arthroplasty. The current study provides a natural history benchmark for clinical outcomes that can be expected in patients with medial meniscus posterior horn root tears undergoing non-operative treatment and helps in counselling patients with these types of injuries. LEVEL OF EVIDENCE: IV.

Long-Term Outcomes after Autologous Chondrocyte Implantation: A Systematic Review at Mean Follow-Up of 11.4 Years.

OBJECTIVE: Autologous chondrocyte implantation (ACI) has not been proven to be durable over the long-term. The purpose of this systematic review was (1) to evaluate activity level and knee function, (2) to evaluate reoperation and failure rates, and (3) to analyze risk factors for reoperation and failure of ACI at minimum long-term follow-up. DESIGN: A comprehensive review was performed for studies with long-term outcomes after ACI for cartilage defect repair. Studies reported outcome scores such as Tegner score, Lysholm score, and International Knee Documentation Society (IKDC) score along with rates of failure and reoperation. Modified Coleman Methodology Scores were calculated to assess study methodological quality. RESULTS: Nine studies with a total of 771 patients with a mean age of 33.4 ± 2.5 years, mean defect size of 5.9 ± 1.6 cm(2), and mean follow-up of 11.4 years were included. Tegner score, Lysholm score, and IKDC score change from preoperative to final follow-up was 1.1 (95% CI 0.8-1.4, P < 0.001), 24.9 points (95% CI 18.8-31, P < 0.001), and 16.5 points (95% CI 5.4-27.5, P < 0.01), respectively. The mean failure and reoperation rates were 18% and 37%, respectively. Increased age and lesion size (>4.5 cm(2)) were significantly correlated with increased risk of reoperation and failure. CONCLUSIONS: Overall, ACI demonstrated successful outcomes in 82% of patients over the long-term. Increased patient age and lesion size greater than 4.5 cm(2) were risk factors for a higher reoperation and failure rate. Nonetheless, this review is limited by heterogeneity in surgical technique, and lesion and patient characteristics.

Distal Femoral Osteotomy: Lateral Opening Wedge Technique.

Coronal limb malalignment is a significant contributor to asymmetric joint wear, gait abnormalities, and the development and progression of degenerative joint disease. Osteotomies about the knee were developed to realign the mechanical axis of the limb to unload the affected compartment. Valgus malalignment is less common than varus malalignment, but can contribute to a variety of clinical conditions, including lateral compartment cartilage defects and arthritis, lateral patellofemoral instability, and medial collateral ligament laxity. In this article, we describe our preferred operative technique for a lateral opening wedge varus-producing distal femoral osteotomy to correct mild to moderate valgus malalignment.

Opening-Wedge Proximal Tibial Osteotomy.

Varus knee malalignment caused by medial compartment arthritis results in progressive asymmetric wear of the tibiofemoral joint. This wear can cause progressively painful gonarthrosis. Surgical methods to address varus knee malalignment include lateral closing-wedge proximal tibial osteotomy, medial opening-wedge osteotomy, and arthroplasty. Medial opening-wedge proximal tibial osteotomy is an effective procedure for restoring proper coronal alignment and reducing knee pain. In this technical note, we present a reproducible technique for proximal tibial osteotomy.

Osteochondral Autograft Transfer Versus Microfracture in the Knee: A Meta-analysis of Prospective Comparative Studies at Midterm.

PURPOSE: To compare microfracture (MFX) and osteochondral autograft transfer (OAT) surgical techniques to determine (1) postoperative activity level, (2) subjective patient outcomes, (3) failure rates, and (4) assess if any lesion characteristics favored one technique over the other. METHODS: A comprehensive review of literature was performed of all studies comparing MFX and OAT. Studies included were all prospective studies that reported on activity-based outcome measures such as Tegner activity scores and subjective outcomes such as the International Knee Documentation Committee score. Failure rates, as determined by the publishing authors, were recorded for each study. Meta-analyses were conducted using a random-effects model. Paired standardized mean differences (Hedges's g to account for small sample bias) were used for continuous outcome measures, and risk ratios (Mantel-Haenszel method for small sample bias) for dichotomous outcome measures. RESULTS: Six prospective studies satisfied the eligibility criteria and included 249 patients (186 male, 120 female) with an average age of 26.4 years and follow-up of 67.2 months. Tegner scores were superior in patients treated with OAT compared with MFX (ΔOAT-MFX for pre-post scores = 0.94 Tegner points, standardized mean difference [SMD] = 0.469, P = .005). Failure rates of MFX were higher than OAT (OAT = 11%, MFX = 32%, risk ratio = 2.42, P < .036). OAT was superior to MFX at 3 years in relation to subjective outcome scores (SMD = 0.404, P = .008). When assessing OAT lesions larger than 3 cm2, OAT was superior to MFX with respect to activity level (SMD = 0.506, P = .001). CONCLUSIONS: OAT may achieve higher activity levels and lower risk of failure when compared with MFX for cartilage lesions greater than 3 cm2 in the knee, although there was no significant difference for lesions less than 3 cm2 at midterm. However, because of variability in patient-specific factors such as age, preinjury activity level, lesion location and size, the superiority of OAT over MFX cannot be generalized to all patient populations and therefore requires individualized patient care. LEVEL OF EVIDENCE: Level II, meta-analysis of Level I and II studies.

Are Short-term Outcomes of Hip Arthroscopy in Patients 55 Years and Older Inferior to Those in Younger Patients?

BACKGROUND: Hip arthroscopy for young patients with femoroacetabular impingement (FAI) has been successful, but the efficacy of hip arthroscopy in older patients is not clearly defined. PURPOSE: To evaluate the clinical outcomes of patients 55 years and older who are undergoing hip arthroscopy and to compare outcomes with those of patients younger than 55 years. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 201 (63 male, 138 female) patients undergoing primary hip arthroscopy for FAI without radiographic arthritis (Tönnis grade <3) were isolated from a prospective database and stratified by age to <55-year and ≥55-year groups. Patients were evaluated preoperatively and 1 and 2 years postoperatively using the modified Harris Hip Score (mHHS) and Hip Outcome Score (HOS: functional scores, as well as Activities of Daily Living [ADL] and Sport subscales). A Wilcoxon signed rank sum test was used to evaluate the differences in outcome scores between the cohorts at each interval. RESULTS: The <55-year group included 174 patients (mean age, 37 ± 12 years), and the ≥55-year group included 27 patients (mean age, 61 ± 5 years). The minimum follow-up time was 2 years in each group. Preoperative Tönnis grades and mHHS scores (59 vs 59; P = .75) were similar between groups. The ≥55-year cohort underwent labral debridement more frequently (78% vs 36%; P =.02) and were more likely to have full-thickness cartilage defects (22% vs 4%; P = .04). Despite this, the mHHS in both groups improved significantly from baseline, without significant differences at 1 year (86 [≥55 years] vs 81 [<55 years]; P = .53) or 2 years (73.88 [≥55 years] vs 79.54 [<55 years]; P = .06). However, at a minimum 2-year follow-up, patients <55 years had significant improvements over patients ≥55 years in the HOS subscales for ADL score (85.6 vs 75.2; P = .03), ADL rating (80.1 vs 70.0; P = .004), Sport score (70.2 vs 55.6; P = .04), and Sport rating (70.2 vs 58.0; P = .04). CONCLUSION: Although younger patients had superior HOS outcomes reported at 2 years compared with older patients after hip arthroscopy for FAI, both groups had significant improvement compared with their baseline. These data suggest that carefully selected patients 55 years and older without radiographic arthritis may benefit from hip arthroscopy.

Long-term Outcomes After Osteochondral Allograft: A Systematic Review at Long-term Follow-up of 12.3 Years.

PURPOSE: To (1) evaluate long-term outcomes of osteochondral allograft (OCA) with regard to clinical outcome scores, reoperation and failure rates, and (2) examine if certain factors predispose patients to worse outcomes. METHODS: A comprehensive review was performed with specific inclusion criteria for studies with long-term outcomes after OCA. Studies reported on patient clinical scores such as Hospital for Special Surgery score, Knee Society Score (knee and function score), and Lysholm score. Reoperation and failure rates were recorded for each study. Modified Coleman Methodology Scores assessed study methodological quality. RESULTS: Five studies with a total of 291 patients (55% male, 45% female) and average age of 34.8 years (range, 15 to 69 years) were included. Of all lesions, 67% were on the femoral condyles, 29% on the tibial plateau, and 4% were patellofemoral. All scores (Knee Society Function Score, Knee Society Knee Score, and Lysholm score) have significant mean improvement from preoperative to final follow-up. The mean postoperative Hospital for Special Surgery score was 84.1. The mean failure rate was 25% at 12.3 years with a reoperation rate of 36%. A total of 72% of the failures were conversion to total (68%) or unicompartmental (4%) knee arthroplasty and 28% involved graft removal, graft fixation, and graft revision. Patellofemoral lesions (83%) had a significantly higher reoperation rate than lesions involving the tibial plateau or the femoral condyles (34%, P = .01). CONCLUSIONS: Overall, OCA demonstrated significant improvements in clinical outcome scores and good durability with successful outcomes in 75% of the patients at 12.3 years after surgery. Patellofemoral lesions are associated with decreased clinical improvement and more frequent reoperations. The orthopaedic literature is limited by heterogeneity in surgical technique, lesion and patient characteristics, and reporting of nonstandardized outcome measures. LEVEL OF EVIDENCE: Level IV, systematic review of Level II and IV studies.

Long-term Outcomes After Osteochondral Autograft Transfer: A Systematic Review at Mean Follow-up of 10.2 Years.

PURPOSE: To evaluate (1) activity level and knee function, (2) reoperation and failure rates, and (3) risk factors for reoperation and failure of osteochondral autograft transfer (OAT) at minimum long-term follow-up. METHODS: A comprehensive review was performed for long-term outcomes after OAT. Studies reported on activity-based outcomes (Tegner Activity Scale) and clinical outcomes (Lysholm score and International Knee Documentation Committee score). Reoperation and failure rates, as defined by the publishing authors, were recorded for each study. Modified Coleman Methodology Scores were calculated to assess study methodological quality. RESULTS: Ten studies with a total of 610 patients with an average age of 27.0 years at the time of surgery and a mean follow-up of 10.2 years were included. The mean defect size was 2.6 cm(2) (range, 0.9 to 20.0 cm(2)). The mean duration of symptoms before surgery was 4.8 years. From preoperative to final follow-up, International Knee Documentation Committee scores and Lysholm scores improved significantly by 42.4 (95% confidence interval [CI], 31.8 to 53.1, P < .001) and 21.1 (95% CI, 12.2 to 30.0, P < .01), respectively. Tegner score did not improve significantly (0.76, 95% CI, -0.83 to 2.36, P = .35). Overall failure rate was 28% and reoperation rate was 19%. Increased age, previous surgery, and defect size positively correlated with increased risk of failure. Concomitant surgical procedures negatively correlated with failure rate. CONCLUSIONS: Overall, OAT showed successful outcomes in 72% of patients at long-term follow-up. Increased age, previous surgery, and defect size correlated positively with failure rate, whereas success improved with concomitant surgical procedures. Nonetheless, this systematic review is limited by heterogeneity in a surgical technique, lesion and patient characteristics, and reporting of nonstandardized outcome measures. LEVEL OF EVIDENCE: Level IV, systematic review of Level I-IV studies.

Does age predict outcome after multiligament knee reconstruction for the dislocated knee? 2- to 22-year follow-up.

PURPOSE: The purpose of this study is to determine whether age is a predictor of clinical and functional outcomes in patients who sustained a knee dislocation (KD) and underwent multiligament knee reconstruction. It was hypothesized that increasing age will negatively affect patient outcome. METHODS: In total, 125 multiligament knee injuries (MLKI) associated with KD were surgically reconstructed between 1992 and 2013 and evaluated with IKDC and Lysholm scores at a median follow-up of 5 (range 2-22) years. Patient demographics including age were then analysed with respect to IKDC and Lysholm scores using rank sums and pair-wise rank sums analysis for continuous variables and Chi-square analysis for categorical variables. RESULTS: In total, 125 patients (96 males and 29 females) with a median age of 31 (range 11-62) years at the time of surgery were included. At final follow-up, patients ≤30 years old compared to >30 years old obtained higher IKDC (73.3 vs. 61.9; p = 0.01) and Lysholm scores (76.9 vs. 68.5; p = 0.04). No confounding variables including gender, injury mechanism, injury pattern, injuries to the peroneal nerve, popliteal artery, meniscus, or cartilage accounted for differences in outcome scores between the two groups. CONCLUSION: Based on current available literature, this study represents the largest cohort with the longest follow-up reported on MLKI to date. At intermediate- to long-term follow-up, patients >30 years of age that undergo multiligament knee reconstruction for KD have inferior IKDC and Lysholm scores compared to those ≤30 years of age. However, successful multiligament knee reconstruction can still be obtained in this age group. LEVEL OF EVIDENCE: IV.

Fiber reference misalignment induced error in cylindrical wave interferometry.

This paper presents an experimental study of fiber reference misalignment induced error in a cylindrical wave test. As with any reference surface, misalignment aberrations are introduced into the measurement when the fiber reference is not perfectly aligned. Given the unique and unusual 1-dimensional filtering properties of the fiber reference, an empirical test was necessary to determine what the actual misalignment sensitivities are. The experimental results and analysis show that the 1-D filtering of the fiber does not affect the misalignment sensitivities. Also, the misalignment sensitivities are smaller, by a factor of two, than values previously reported for cylindrical test misalignment sensitivities. The sensitivities presented in this paper can be used to correctly realign a misaligned fiber reference in the lab.

Creating and Closing the T-Capsulotomy for Improved Visualization During Arthroscopic Treatment of Femoroacetabular Impingement.

Treatment of femoroacetabular impingement through an arthroscopic approach has gained widespread popularity in recent years. Although outcomes are generally favorable, one of the most common reasons for failure is incomplete resection of cam lesions of the femoral neck. As a result, the T-capsulotomy has been introduced as a method for improving access to the femoral head-neck junction, which is not always visible through a standard interportal capsulotomy. The T-capsulotomy has the benefits of improving arthroscopic visualization of the femoral neck, reducing overall fluoroscopy exposure for the patient and surgeon, and facilitating capsular plication. We present a reliable and efficient method for creating and repairing the T-capsulotomy. We routinely perform this technique in patients with cam lesions that are too large or too distal to safely visualize and decompress through an interportal capsulotomy.

A Simple Technique for Capsular Repair After Hip Arthroscopy.

Capsulotomy is typically performed during arthroscopic treatment for femoroacetabular impingement. As the frequency of hip arthroscopy continues to expand rapidly, increased attention is being paid to the implications of interportal capsulotomy and the need for repair. To minimize the risk of postoperative instability, capsular closure has been recommended to restore the anatomy and biomechanical function of the capsule. We present a reliable, efficient, and effective method for arthroscopic closure of the interportal capsulotomy after hip arthroscopy.

Separating misalignment from misfigure in interferograms on cylindrical optics.

This paper presents an analytical method that allows for unambiguous separation of misalignment from the interferometric measurement of cylindrical optics with rectangular apertures. This method not only removes the misalignment-induced aberration from the measured wavefront data, but also yields the amount of misalignment in the test setup. We verified this method during testing of a convex cylindrical optic.

Transmissive quasi-optical Ronchi phase grating for terahertz frequencies.

A transmissive, square-wave Ronchi phase grating has been fabricated from the dielectric polytetrafluoroethylene to diffract an ~0.7 THz beam quasi-optically. When illuminated by a coherent, cw terahertz (THz) source, the spot separation of the ±1 diffractive orders and the diffraction efficiency were measured as a function of THz frequency and rotation angle. The grating performance depends sensitively on the refractive index, whose value can be measured with an accuracy limited by the fabrication precision. The use of these gratings for polarization-insensitive quasi-optical imaging and phased arrays is discussed.