Improved Patient-reported Outcomes in Patients Aged 16 and Younger at Two Years After Anterior Cruciate Ligament Reconstruction Despite Relatively High Rates of Reinjury and Repeat Surgery.

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) in adolescent patients, particularly those aged 16 and under, are increasingly common procedure that lacks robust clinical and patient-reported outcome (PRO) data. The purpose of this study was to report 2-year PROs of patients receiving ACLR aged 16 or younger using the single assessment numerical evaluation (SANE) and knee injury and osteoarthritis outcome score (KOOS). Secondary aims included characterizing treatment characteristics, return to sport (RTS), and clinical outcomes. METHODS: The institutional PRO database was queried for patients receiving ACLR from 2009 to 2020. Patients aged older than 16, revision procedures, concomitant ligament repairs/reconstructions, and patients without full outcome data at 2 years were excluded. Outcomes over 2 years after ACLR included SANE, KOOS, reinjuries, reoperations, and time to RTS. RESULTS: A total of 98 patients were included with an average age of 15.0 years. Most patients were females (77.6%). Bone-tendon-bone autograft (69.4%) was the most used. Average RTS was 8.7 months (range: 4.8 to 24.0 mo), with 90% of patients eventually returning to sport. A total of 23 patients (23.5%) experienced a reinjury and 24.5% (n = 24) underwent reoperation. Timing to RTS was not associated with reinjury, but patients who returned between 9.5 and 13.7 months did not sustain reinjuries. Mean KOOS and SANE scores at 2 years were 87.1 and 89.1, respectively, with an average improvement of +18.4 and +22.9, respectively. Change in KOOS was negatively impacted by reinjury to the anterior cruciate ligament graft and reoperation (anterior cruciate ligament failure: +10.0 vs 19.3, P = 0.081, respectively; reoperation: +13.2 vs +20.1, P = 0.051, respectively), though these did not reach statistical significance. CONCLUSION: Patients experienced improved SANE and KOOS scores after ACLR. Rates of reinjury and reoperation were relatively high and negatively impacted PRO scores but were not associated with the timing of RTS. Adolescent patients should be counseled regarding the risk of subsequent ipsilateral and contralateral knee injury after ACLR. LEVEL OF EVIDENCE: Level IV-case series.

What Is the Survivorship After Hip Arthroscopy for Femoroacetabular Impingement? A Large-database Study.

BACKGROUND: Patients with femoroacetabular impingement (FAI) may experience lasting clinical improvement after hip arthroscopy; however, some patients will still eventually undergo early conversion to THA due to unresolved symptoms and progression of arthritis. However, the risk of this has been only incompletely characterized in prior studies. QUESTIONS/PURPOSES: Using a large healthcare claims database over a 5-year period (2011-2016), we asked: (1) What is the survivorship free from THA after arthroscopic osteoplasty performed for FAI? (2) What identifiable demographic factors and patient characteristics are associated with early conversion to THA after hip arthroscopy performed for FAI? METHODS: We included all patients who underwent hip arthroscopy for FAI, between the ages of 12 years and 63 years, with 3 months of claims data before hip arthroscopy and minimum 2-year follow-up. A total of 4730 hip arthroscopy patients from 2011 to 2014 were retrieved from a US commercial claims database. Hip arthroscopy incidence doubled over time from 1.2 to 2.1 persons per 100,000. Temporal trends, patient demographics, diagnoses at time of arthroscopy, and patient comorbidities were retrieved and logistic regression performed. Survivorship analysis on 11,323 patients (lifting the 2-year follow-up requirement) was also performed to identify independent variables associated with early risk of conversion to THA. RESULTS: In patients undergoing hip arthroscopy for FAI, the overall proportion of conversion to THA within 2 years after hip arthroscopy was 7% (338 of 4730). After controlling for confounding variables such as sex, obesity, and depression, we found the following were independently associated with increased odds of conversion to THA: older age (odds ratio 1.08 [95% CI 1.01 to 1.10]; p < 0.001), osteoarthritis (OR 2.91 [95% CI 2.27 to 3.77]; p < 0.001), joint inflammation (OR 1.89 [95% CI 1.16 to 3.09]; p = 0.01), and a history of opioid use (OR 2.17 [95% CI 1.69 to 2.79]; p < 0.001). Survivorship analysis similarly revealed that older age (hazard ratio 1.08 [95% CI 1.07 to 1.09]; p < 0.001), osteoarthritis (HR 2.53 [95% CI 2.13 to 3.01]; p < 0.001), joint inflammation (HR 1.53 [95% CI 1.10 to 2.11]; p = 0.01), a history of opioid use (HR 2.02 [95% CI 1.71 to 2.38]; p < 0.001), and smoking (HR 1.55 [95% CI 1.14 to 2.11]; p = 0.005), were independently associated with increased odds of conversion to THA within 2 years after hip arthroscopy for FAI. CONCLUSIONS: Although the findings of this study are limited and should not be taken in isolation, patients with FAI who are older, carry diagnoses of inflammatory or degenerative articular disease, or who use opioids or smoke should be counseled about a potentially increased risk of undergoing early conversion to THA after hip arthroscopy. Future studies to further examine the effect of these diagnoses in prospectively collected cohorts, incorporating radiographic and patient-reported outcome measures, are needed. LEVEL OF EVIDENCE: Level III, prognostic study.

Limited Return to Preinjury Performance in NCAA Division I American Football Players With Hamstring Injuries.

Background: Hamstring strains are common among elite athletes, but their effect on return to the same level of play in American football has been incompletely characterized. Purpose: Data on National Collegiate Athletics Association Division I college football players with acute hamstring strains were gathered to identify the effects these injuries have on both return to play and athletic performance regarding velocity, workload, and acceleration. Study Design: Case Series; Level of evidence, 4. Methods: Injury data for a single Division I football team were prospectively recorded over a 4-year period. Players wore global navigation satellite system and local positioning system (GNSS/LPS) devices to record movement data in practices and games. The practice and game data were cross-referenced to evaluate players with isolated acute hamstring strains. Comparisons were made regarding players' pre- and postinjury ability to maintain high velocity (>12 mph [19.3 kph]), maximal velocity, triaxial acceleration, and inertial movement analysis (IMA). There were 58 hamstring injuries in 44 players, of which 25 injuries from 20 players had GNSS/LPS data. Results: Players were able to return to play from all 25 injury incidences at a mean of 9.2 days. At the final mean follow-up of 425 days, only 4 players had reached preinjury function in all measurements; 12 players were able to return in 2 of the 4 metrics; and only 8 players reached their preinjury ability to maintain high velocity. For those who did not achieve this metric, there was a significant difference between pre- and postinjury values (722 vs 442 m; P = .016). A total of 14 players were able to regain their IMA. Players who returned to prior velocity or acceleration metrics did so at a mean of 163 days across all metrics. Conclusion: While players may be able to return to play after hamstring strain, many players do not reach preinjury levels of acceleration or velocity, even after 13.5 months. Further studies are needed to confirm these findings, assess clinical relevance on imaging performance, and improve hamstring injury prevention and rehabilitation.

Reconstructing a Patellar Tendon Rupture Neglected for 14 Years When Anatomic Restoration Is Not Possible: A Case Report.

CASE: This case highlights the utility and outcomes of an Achilles tendon bone-block allograft in reconstructing the patellar tendon of a 44-year-old man in the setting of a high-riding, irreducible patella after a chronic patellar tendon rupture of 14 years. CONCLUSION: In cases of a neglected patellar tendon rupture with an irreducible high-riding patella, an Achilles tendon bone-block allograft can provide the length and tissue necessary to reconstruct the extensor mechanism. Although reconstruction may not be anatomic, patients can still experience great subjective and objective functional improvement with restoration of the extensor mechanism even after delayed reconstruction.

Effect of Increased Time to Surgery on the Ability of MRI to Rule Out Medial Meniscal Tears in Young Athletes With ACL Injury.

Background: The prevalence of meniscal tears in patients with anterior cruciate ligament (ACL) injury increases with extended time between injury and ACL reconstruction. Purpose/Hypothesis: The purpose of this study was to determine if there is a relationship between time from magnetic resonance imaging (MRI) to ACL reconstruction and the predictive value of MRI to diagnose meniscal tears in the young active population. It was hypothesized that increased time between MRI and ACL reconstruction would lead to a decrease in the negative predictive value of MRI in diagnosing meniscal tears, as more injuries may accrue over time in the ACL-deficient knee. Study Design: Case series; Level of evidence, 4. Methods: Included were patients aged 13 to 25 years at the authors' institution who underwent primary ACL reconstruction from January 2017 to June 2020. Time from MRI to surgery as well as descriptions of medial and lateral meniscal tears on both MRI and operative reports were documented. Time from MRI to surgery was divided into 4 intervals: 0 to 6 weeks, >6 weeks to 3 months, >3 to 6 months, and beyond 6 months. Multivariable analysis was used to determine the positive and negative predictive values of MRI in diagnosing a meniscal tear as compared with arthroscopic findings. Results: A total of 432 patients were included with a mean age of 17.9 ± 3.4 years. The mean time from MRI to surgery was 70.5 ± 98 days. There was a significant decrease in the negative predictive value of MRI to identify a medial meniscal tear in patients who underwent ACL reconstruction >6 months after imaging (odds ratio, 0.16 [95% CI, 0.05-0.53]; P = .003). This same relationship was not shown for lateral meniscal tears, nor was any other predictor significant. Conclusion: The utility of MRI to rule out a medial meniscal tear significantly diminished in the young athletic population when >6 months passed between MRI and ACL reconstruction. These data suggest these tears occur between the time of the MRI and surgery and that the medial meniscus is more susceptible than the lateral meniscus to new injury once the ACL has torn.

Autograft patellar bone-tendon-bone use does not increase operative time in anterior cruciate ligament reconstruction.

Background: Anterior cruciate ligament reconstruction (ACLR) is a common procedure that has been shown to have relatively good outcomes amongst various graft types. Operative time in ACLR has been found to influence outcomes and cost. The purpose of this study was to evaluate the association of operative time in primary arthroscopically performed anterior cruciate ligament reconstruction (ACLR) and graft type while controlling for confounders that influence time. Methods: All patients who received ACLR between 2018 and 2022 were included in this retrospective cohort study. Exclusion criteria consisted of age (≤16 years), revisions, concomitant ligament reconstruction or tendon repairs, or other simultaneously performed procedures that could potentially add substantial variation in operative time. The primary outcome was operative time. Graft types included allograft, bone-tendon-bone (BTB) autograft, hamstring tendon (HS) autograft and quadriceps tendon (QT) autograft. Results: A total of 1813 primary ACLRs were included. The average operative time was 98.9 ± 33.0 min. Graft utilization varies considerably among surgeons. The most used graft type was BTB autograft (42.6%) followed by HS autograft (32.3%) and allograft (21.4%). Only 68 cases (3.8%) used a QT autograft. Seven of the 15 included surgeons primarily used BTB autograft. One surgeon predominately used QT autograft. No difference in operative time was observed among the autograft types (p = 0.342). Allograft ACLR was significantly faster by 27-33 min compared to using BTB autograft, HS autograft, or QT autograft (p < 0.001). Conclusion: Operative time did not vary by type of autograft selected. Allograft ACLR was performed approximately 30 min faster than autograft ACLR. Further studies examining the effect on patient outcomes of reduced operative time and minimizing graft harvest morbidity in ACLR is important to more accurately determine the cost-effectiveness of allograft ACLR.

Anterior Cruciate Ligament Reconstruction with 4-Strand Hamstring Tendon Construct May be Biomechanically Superior to 5-Strand Hamstring Tendon Construct When Using Femoral Suspensory Fixation.

Purpose: To compare stiffness, strain, and load to failure of 4- versus 5-strand hamstring anterior cruciate ligament reconstruction human tendon allografts with femoral suspensory and tibial interference screw fixation. Methods: Allograft hamstring tendons were used to create 10 four-strand (4S) and 10 five-strand (5S) grafts. Grafts were fixed to a uniaxial electromechanical load system via a femoral cortical suspensory button and a bioabsorbable interference screw in bone analogue. Grafts were cycled from 100 Newtons (N) to 250 N for 1,000 repetitions at 0.5 hertz before load to failure testing. Cyclic displacement was defined as the difference in graft length from the first 20 to 30 cycles compared with the last 10 cycles. Trials were recorded on a high-definition camera to allow for digital image correlation analysis. Results: Cyclic displacement more than 1,000 cycles was significantly lower in the 4S compared with the 5S group (0.87 vs 1.11 mm, P = .037). Digital image correlation analysis confirmed that the fifth strand elongated more than the other 4 strands in the 5S constructs (6.1% vs 3.9%, P = .032). Load to failure was greater in the 4S compared with the 5S group but not statistically significant (762 vs 707 N, P = .35). Stiffness was similar between constructs (138.5 vs 138.3 N/mm, P = .96). Conclusions: Compared with cyclically loaded 4S hamstring grafts, the 5S grafts had significantly increased displacement over time in a model of femoral suspensory and tibial interference screw fixation. Clinical Relevance: Anterior cruciate ligament reconstruction with hamstring tendon autograft is a commonly performed surgery with excellent outcomes. It has been shown that graft diameter influences these outcomes. As surgeons use larger grafts, it is important to investigate how these constructs may affect the outcomes of surgery.

Does the Preferred Study Source Impact Orthopedic In-Training Examination Performance?

OBJECTIVE: This study examines the role of electronic learning platforms for medical knowledge acquisition in orthopedic surgery residency training. This study hypothesizes that all methods of medical knowledge acquisition will achieve similar levels of improvement in medical knowledge as measured by change in orthopedic in-training examination (OITE) percentile scores. Our secondary hypothesis is that residents will equally value all study resources for usefulness in acquisition of medical knowledge, preparation for the OITE, and preparation for surgical practice. DESIGN: 9 ACGME accredited orthopedic surgery programs participated with 95% survey completion rate. Survey ranked sources of medical knowledge acquisition and study habits for OITE preparation. Survey results were compared to OITE percentile rank scores. PARTICIPANTS: 386 orthopedic surgery residents SETTING: 9 ACGME accredited orthopaedic surgery residency programs RESULTS: 82% of participants were utilizing online learning resources (Orthobullets, ResStudy, or JBJS Clinical Classroom) as primary sources of learning. All primary resources showed a primary positive change in OITE score from 2018 to 2019. No specific primary source improved performance more than any other sources. JBJS clinical classroom rated highest for improved medical knowledge and becoming a better surgeon while journal reading was rated highest for OITE preparation. Orthopedic surgery residents' expectation for OITE performance on the 2019 examination was a statistically significant predictor of their change (decrease, stay the same, improve) in OITE percentile scores (p<0.001). CONCLUSIONS: Our results showed that no specific preferred study source outperformed other sources. Significantly 82% of residents listed an online learning platform as their primary source which is a significant shift over the last decade. Further investigation into effectiveness of methodologies for electronic learning platforms in medical knowledge acquisition and in improving surgical competency is warranted.

Biomechanical Effects of Blood Flow Restriction Training after ACL Reconstruction.

INTRODUCTION: After anterior cruciate ligament reconstruction surgery, returning the knee to previous levels of strength and function is challenging, with the failure to do so associated with an increased risk of reinjury and long-term degenerative problems. Blood flow restriction (BFR) is gaining popularity as a rehabilitation technique; however, its effects on the mechanics of these exercises have not been fully explored. In this study, we aimed to determine the acute effects of BFR on the performance of a step-up exercise protocol and to assess the acceptability of the technique. METHODS: Twenty individuals (12 female/8 male; mean age, 30.6 yr) who had recently undergone anterior cruciate ligament reconstruction and 20 controls (11 female/9 male, mean age 28.0 yr) performed a step-up exercise protocol with and without BFR. Lower limb kinematics and kinetics were measured and compared between groups and conditions. Testing was completed in June 2019. RESULTS: Participants in both groups had increased external rotation of the tibia of 2° (P < 0.001) and reductions in knee flexion and rotation torques around the joint of around 50% (P < 0.001) when using BFR compared with nonrestricted step-up exercise. The intervention was found to increase the difficulty of the exercise and induce moderate levels of discomfort (P < 0.001). CONCLUSION: The present study provides cautious support for the use of BFR, showing that there are minimal changes in knee joint mechanics when performing the same exercise without BFR, and that the changes do not increase joint torques at the knee. From an acute biomechanical perspective, the intervention appears safe to use under qualified supervision; however, effects of repetitive use and long-term outcomes should be monitored.

Preoperative MRI for the Multiligament Knee Injury: What the Surgeon Needs to Know.

The multiligament knee injury is devastating and potentially limb threatening. Preoperative magnetic resonance imaging for the evaluation of the multiligament knee injury is an invaluable clinical tool, and when the radiologist is familiar with how certain injury patterns influence management, optimal outcomes can be achieved. We provide a detailed description of the relationship between salient imaging features of the multiligament knee injury, focusing on the preoperative magnetic resonance imaging, and their influence on clinical decision-making.

Trends in Race/Ethnicity Among Applicants and Matriculants to US Surgical Specialties, 2010-2018.

Importance: Surgical programs across the US continue to promote and invest in initiatives aimed at improving racial/ethnic diversity, but whether this translates to changes in the percentage of applicants or matriculants from racial/ethnic minority groups remains unclear. Objective: To examine trends in the percentage of applicants and matriculants to US surgical specialties who identified as part of a racial/ethnic group underrepresented in medicine from the 2010-2011 to 2018-2019 academic years. Design, Setting, and Participants: This cross-sectional study examined trends in self-reported racial/ethnic identity among applicants and matriculants to US residency programs to evaluate demographic changes among surgical programs from 2010 to 2018. Data were obtained from the Association of American Medical Colleges. Results: The study population consisted of a total of 737 034 applicants and 265 365 matriculants to US residency programs, including 134 158 applicants and 41 347 matriculants to surgical programs. A total of 21 369 applicants (15.9%) and 5704 matriculants (13.8%) to surgical specialties identified as underrepresented in medicine. There was no statistically significant difference in the percentage of applicants underrepresented in medicine based on race/ethnicity for all surgical specialties combined in 2010 vs 2018 (15.3% [95% CI, 14.7%-15.9%] vs 17.5% [95% CI, 16.9%-18.1%]; P = .63). Thoracic surgery was the only surgical specialty in which there was a statistically significant change in the percentage of applicants (8.1% [95% CI, 4.9%-13.2%] vs 14.6% [95% CI, 10.2%-20.4%]; P = .02) or matriculants (0% [95% CI, 0%-19.4%] vs 10.0% [95% CI, 4.0%-23.1%]; P = .01) underrepresented in medicine based on race/ethnicity. Obstetrics and gynecology had the highest mean percentage of applicants (20.2%; 95% CI, 19.4%-20.8%) and matriculants (19.0%; 95% CI, 18.2%-19.8%) underrepresented in medicine among surgical specialties. Thoracic surgery had the lowest mean percentage of applicants (12.5%; 95% CI, 9.46%-15.4%) and otolaryngology the lowest mean percentage of matriculants (8.5%; 95% CI, 7.2%-9.9%) underrepresented in medicine. Conclusions and Relevance: In this cross-sectional study, overall US surgical programs had no change in the percentage of applicants or matriculants who self-identified as underrepresented in medicine based on race/ethnicity, but the proportion remained higher than in nonsurgical specialties. Reevaluation of current strategies aimed at increasing racial/ethnic representation appear to be necessary to help close the existing gap in medicine and recruit a more racially/ethnically diverse surgical workforce.

Monitoring changes in knee surface morphology after anterior cruciate ligament reconstruction surgery using 3Dsurface scanning.

STUDY DESIGN: Prospective case series. BACKGROUND: After surgical reconstruction of the anterior cruciate ligament, recovery to pre-injury levels of knee function is challenging. Postoperative edema and muscle atrophy are common roadblocks to full function and are evident in changes to the surface morphology of the knee. There are currently few accessible objective tools to accurately track these morphological changes. OBJECTIVES: We aimed to determine if 3D surface scanning can be used to monitor changes in the external shape of the knee after surgery and throughout the rehabilitation process. METHODS: Thirty participants had 3D surface scans taken of their knee, along with questionnaire-based functional outcomes prior to surgery (baseline), and at two-week, six-week, 12-week, and 26-week timepoints post-surgery. Volumetric changes relative to pre-op were assessed using generalized linear growth models for key anatomical regions and correlated with functional outcomes. RESULTS: Significant swelling of the patella region compared to baseline was evident immediately after surgery (14%, p < 0.001), before returning to pre-operative levels. Changes in volume at this region were significantly associated with patient-reported functional outcomes. Reductions in volume of the regions corresponding to the vastus medialis and lateralis muscles were significant at 12 weeks post-surgery (p = 0.018 and 0.01 respectively) but returned to baseline levels at six months. CONCLUSION: We demonstrate the use of 3D surface scanning as a method for capturing detailed measurements of knee surface morphology after surgery. Significant changes in external morphology are evident during the rehabilitation process.

THE USE OF MICROSOFT KINECT ™ FOR ASSESSING READINESS OF RETURN TO SPORT AND INJURY RISK EXERCISES: A VALIDATION STUDY.

INTRODUCTION: Assessing readiness of return to sport after procedures such as anterior cruciate ligament (ACL) reconstruction is a complex process, complicated by the pressures that athletes face in returning to sport as quickly as possible. Advances in motion analysis have been able to demonstrate movements that are risk factors for initial ACL injury and subsequent reinjury after reconstruction. An inexpensive, objective measure is needed to determine when athletes are ready to return to sport after ACL reconstruction. PURPOSE: The aim of this study was to compare the use of a single camera, markerless motion capture technology to 3D motion capture during lower extremity movements that pose as risk factors for ACL injury. STUDY DESIGN: Cross Sectional Study. METHODS: This study assessed the validity of the Microsoft Kinect™ against an established 3-dimensional motion analysis system in 20 healthy subjects. Knee kinematics were assessed during impact activity in the coronal and sagittal plane specifically evaluating peak knee valgus and peak knee flexion during single leg hop and jump from box exercises. Intraclass correlation coefficients and 95% limits of agreement (LoA) were determined for each kinematic variable. RESULTS: For the single leg hop, the mean absolute difference in the sagittal plane was 10.4 ° (95% LoA [-11.7 °, 26.8 °]), and in the frontal plane was 5.31 ° (95% LoA [-8 °, 13.9 °]). Similarly, for the jump from box landing on one leg, there was a difference of 7.96 ° (95% LoA [-17.7 °, 21.3 °]) and 4.69 ° (95% LoA [-6.3 °, 12.6 °]) respectively. For the jump from box, two-foot land, turn and pivot, the mean absolute difference between the systems was 7.39 ° (95% LoA [-17.8 °, 19.7 °]) in the sagittal and 4.22 ° (95% LoA [-5.9 °, 11.6 °]) in the frontal plane respectively. Intraclass correlation coefficients for each activity ranged from 0.553 to 0.759. CONCLUSION: The results from the Microsoft Kinect™ were found to be in poor agreement with those from a standard motion capture system. Measuring complex lower extremity movements with the Microsoft Kinect™ does not provide adequate enough information to use as an assessment tool for injury risk and return to sport timing. LEVEL OF EVIDENCE: Level III.

The Menstrual Cycle May Affect Anterior Knee Laxity and the Rate of Anterior Cruciate Ligament Rupture: A Systematic Review and Meta-Analysis.

BACKGROUND: Women have a higher risk of anterior cruciate ligament (ACL) tears than men, the causes of which are multifactorial. The menstrual cycle and its hormonal effect on the knee may contribute to knee laxity and ACL injury. This work reviewed published studies examining the effects of the phases of the menstrual cycle on anterior knee laxity and the rate of ACL tears. METHODS: A systematic review with meta-analysis and meta-regression was performed. Studies with data comparing the menstrual cycle phase with ACL injury or anterior knee laxity were included for analysis. Data with regard to patient demographic characteristics, anterior knee laxity, ACL injury, and menstrual cycle phases were extracted from the included studies. RESULTS: In this study, 1,308 search results yielded 396 articles for review, of which 28 met inclusion criteria. Nineteen studies of knee laxity with 573 combined subjects demonstrated a mean increase in laxity (and standard deviation) of 0.40 ± 0.29 mm in the ovulatory phase compared with the follicular phase and a mean increase in laxity of 0.21 ± 0.21 mm in the luteal phase compared with the follicular phase. Nine studies examining ACL tears with 2,519 combined subjects demonstrated a decreased relative risk (RR) of an ACL tear in the luteal phase compared with the follicular and ovulatory phases combined (RR, 0.72 [95% confidence interval, 0.56 to 0.89]). There were no differences in ACL tear risk between any of the other phases. CONCLUSIONS: An increased risk of an ACL tear does not appear to be associated with periods of increased laxity in this meta-analysis. Although this suggests that hormonal effects on an ACL tear may not be directly related to increases in knee laxity, the methodologic heterogeneity between published studies limits the conclusions that can be drawn and warrants further investigation. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Pull Test: A Dynamic Test to Confirm Hip Microinstability.

PURPOSE: To define a distraction distance (pull length) cut-off that would differentiate those patients with hip microinstability and those without the disorder, called the Pull-Out Test. METHODS: In total, 100 consecutive patients undergoing hip arthroscopy were included in the study. Patients were separated into a hip microinstability group (HMI) and non-hip microinstability group (NHI) based on the results of Beighton's score, the abduction-extension-external rotation test, hip extension-external rotation examination, and the prone instability test. Inclusion criteria were patients with an magnetic resonance imaging-proven labral tear who did not respond to conservative treatment and underwent hip arthroscopy. Exclusion criteria included those patients undergoing revision hip arthroscopy, had a previous surgery on the ipsilateral hip, or had severe arthritis in the hip. The Pull-Out Test was performed before surgery with the hip in 30° of abduction and the foot in 30° of external rotation. A blinded examiner places gross axial traction on the leg until a firm end point is reached. The distraction distance between the femoral head and acetabulum is the pull length. RESULTS: In total, 32 patients made up the HMI group whereas 68 patients were in the NHI group. The average pull length for the NHI group was 0.9 ± 0.1 cm and 1.7 ± 0.4 cm for the HMI group (P < .001). Subtracting the standard deviation from the HMI group average, when defined a cut off for hip microinstability as 1.3 cm. Using this value, we found the Pull-Out Test to have a sensitivity of 0.91 and specificity of 0.96. The positive predictive value for the Pull Test was 0.91 and the negative predictive value 0.97. CONCLUSIONS: The Pull-Out Test is a useful test in identifying and confirming the presence of hip microinstability in patients undergoing hip arthroscopy. A pull-length of 1.3 cm or greater is consistent with the presence of microinstability with a specificity of 94% and a sensitivity of 96%. LEVEL OF EVIDENCE: Level IV, diagnostic, case-control study.

Comparison of medial and lateral posterior femoral condyle articular cartilage wear patterns.

BACKGROUND: While degenerative changes to the articular cartilage of the anterior and distal portions of the femoral condyles have been well studied in the literature, the changes that occur on the posterior femoral condyle are not as clear. The purpose of this study was to assess the difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in knees undergoing unicompartmental knee arthroplasty. METHODS: A retrospective review of prospectively gathered data on 107 consecutive patients undergoing unicompartmental knee arthroplasty performed by a single surgeon was performed. The remaining articular cartilage thickness after resection of the posterior femoral condyle was measured and simple analysis conducted to compare cartilage thickness between medial and lateral posterior femoral condyles. RESULTS: Ninety-two medial unicompartmental arthroplasties and 15 lateral unicompartmental arthroplasties were performed during the 16 month study period. The majority of lateral UKA patients were female and had lower BMI than medial UKA patients. The articular cartilage thickness on the medial posterior femoral condyle was 3 mm ±â€¯1 mm (mean ±â€¯standard deviation) and 1 mm ±â€¯1 mm on the lateral side (p-value <0.001). CONCLUSIONS: There is a significant difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in patients undergoing unicompartmental knee arthroplasty. This coincides with a potentially inherently different pattern of articular cartilage degeneration between the medial and lateral compartments of the knee and has implications on implant designs and resurfacing techniques about the knee.