Scope of the Problem: Tendoscopy and Small Joint Arthroscopy of the Foot and Ankle.

It is important to identify and describe practical applications of arthroscopy in the management of foot and ankle pathology. Utilization of the arthroscope provides a minimally invasive means of evaluating and addressing pathology. It obviates the need for a large open approach, which has additional value in the setting of a multiprocedure surgery. In addition to reducing surgical time, arthroscopy provides a potentially enhanced field of view and an adequate working space to address injury. As interest in minimally invasive options grows, the need for safe, effective tendoscopic and arthroscopic options in the foot and ankle increases. A clear and high-yield reference is needed with which to approach these procedures.

Low Level of Evidence and Methodologic Quality of Clinical Outcome Studies on Cartilage Repair of the Ankle.

PURPOSE: To examine the level of evidence and methodologic quality of studies reporting surgical treatments for osteochondral lesions of the ankle. METHODS: A search was performed using the PubMed/Medline, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Cochrane databases for all studies in which the primary objective was to report the outcome after surgical treatment of osteochondral lesions of the ankle. Studies reporting outcomes of microfracture, bone marrow stimulation, autologous osteochondral transplantation, osteochondral allograft transplantation, and autologous chondrocyte implantation were the focus of this analysis because they are most commonly reported in the literature. Two independent investigators scored each study from 0 to 100 based on 10 criteria from the modified Coleman Methodology Score (CMS) and assigned a level of evidence using the criteria established by the Journal of Bone and Joint Surgery. Data were collected on the study type, year of publication, number of surgical procedures, mean follow-up, preoperative and postoperative American Orthopaedic Foot & Ankle Society score, measures used to assess outcome, geography, institution type, and conflict of interest. RESULTS: Eighty-three studies reporting the results of 2,382 patients who underwent 2,425 surgical procedures for osteochondral lesions of the ankle met the inclusion criteria. Ninety percent of studies were of Level IV evidence. The mean CMS for all scored studies was 53.6 of 100, and 5 areas were identified as methodologically weak: study size, type of study, description of postoperative rehabilitation, procedure for assessing outcome, and description of the selection process. There was no significant difference between the CMS and the type of surgical technique (P = .1411). A statistically significant patient-weighted correlation was found between the CMS and the level of evidence (r = -0.28, P = .0072). There was no statistically significant patient-weighted correlation found between the CMS and the institution type (r = 0.05, P = .6480) or financial conflict of interest (r = -0.16, P = .1256). CONCLUSIONS: Most studies assessing the clinical outcomes of cartilage repair of the ankle are of a low level of evidence and of poor methodologic quality. LEVEL OF EVIDENCE: Level IV, systematic review of Level I through IV studies.

Administration of Prophylactic Enoxaparin on the Morning of Surgery Does Not Increase Risk of Blood Transfusion or Wound Drainage Following Internal Fixation of Geriatric Femur Fractures.

BACKGROUND: Despite standard use of chemoprophylaxis, 30-day incidence of venous thromboembolism after geriatric, those older than 60 years, femur fracture surgery is reported to be up to 10%. Missing one dose of enoxaparin has been proven to increase the risk of developing venous thromboembolism. It is commonplace to hold preoperative chemoprophylaxis the morning of surgery because of concern for intraoperative bleeding or wound drainage. We sought to determine whether administration of prophylactic enoxaparin the morning of surgery resulted in an increased rate of blood transfusion or wound drainage in geriatric patients undergoing femur fracture treatment. METHODS: We retrospectively reviewed patients older than 60 years who underwent internal fixation of an isolated femur fracture, including femoral neck, intertrochanteric, subtrochanteric, femoral shaft, and distal femur fractures, at a Level 1 trauma center. Medical records, hospital billing data, and radiographs were reviewed to determine patient characteristics such as Charlson Comorbidity Index, enoxaparin dosing, packed red blood cell transfusion, and persistent wound drainage, defined as any drainage requiring utilization of closed incision negative pressure wound therapy. Thirty-day mortality served as the secondary outcome measure. RESULTS: Five hundred seven patients were included. One hundred sixty-four (32%) received enoxaparin on the morning of surgery, whereas 343 (68%) did not. 27% of patients received PRBC transfusion, and this did not differ between groups (27% vs. 28%, P = 0.72). Subgroup analysis of fixation strategies revealed no difference in the frequency of blood transfusion for any fixation type as related to the timing of enoxaparin dosage. Utilization of closed incision negative pressure wound therapy for the treatment of postoperative wound drainage did not differ between dosing groups. No difference was observed in thirty-day mortality between groups (2.4% vs. 2.7%, P = 0.9). DISCUSSION: Administration of a prophylactic dose of enoxaparin on the morning of surgery does not seem to increase the rate of postoperative blood transfusion or wound drainage after fixation of geriatric femur fracture. LEVEL OF EVIDENCE: Level III, therapeutic.

Achilles Rupture in the Setting Posterior Tibial Osteochondroma: A Case Report and Guidelines for Management of Osteochondromas Adjacent to Tendons.

Introduction: The presentation of the included patient is unique, and the thought process regarding management algorithms used to manage this patient is important to discuss so that other surgeons may benefit. This is the first report of its kind, to our knowledge. Case Report: A 30-year-old healthy Caucasian male presented with acute Achilles tendon rupture after feeling a pop while playing basketball, in the setting of a known posterior tibial osteochondroma and a recent increase in physical activity. Conclusion: The resultant injury is likely due to mechanical irritation at the tendon site, which caused wear over time and eventual acute rupture. We expanded our percutaneous repair to include an evaluation of the posterior compartment to adequately visualize and excise the large bony lesion. Therefore, we conclude that it is reasonable to counsel patients with known osteochondromas in this location due to the risk of possible Achilles injury, particularly if at all symptomatic.

Wearable sensor and machine learning accurately estimate tendon load and walking speed during immobilizing boot ambulation.

Achilles tendon injuries are treated with progressive weight bearing to promote tendon healing and restore function. Patient rehabilitation progression are typically studied in controlled, lab settings and do not represent the long-term loading experienced during daily living. The purpose of this study is to develop a wearable paradigm to accurately monitor Achilles tendon loading and walking speed using low-cost sensors that reduce subject burden. Ten healthy adults walked in an immobilizing boot under various heel wedge conditions (30°, 5°, 0°) and walking speeds. Three-dimensional motion capture, ground reaction force, and 6-axis inertial measurement unit (IMU) signals were collected per trial. We used Least Absolute Shrinkage and Selection Operator (LASSO) regression to predict peak Achilles tendon load and walking speed. The effects of using only accelerometer data, different sampling frequency, and multiple sensors to train the model were also explored. Walking speed models outperformed (mean absolute percentage error (MAPE): 8.41 ± 4.08%) tendon load models (MAPE: 33.93 ± 23.9%). Models trained with subject-specific data performed significantly better than generalized models. For example, our personalized model that was trained with only subject-specific data predicted tendon load with a 11.5 ± 4.41% MAPE and walking speed with a 4.50 ± 0.91% MAPE. Removing gyroscope channels, decreasing sampling frequency, and using combinations of sensors had inconsequential effects on models performance (changes in MAPE < 6.09%). We developed a simple monitoring paradigm that uses LASSO regression and wearable sensors to accurately predict Achilles tendon loading and walking speed while ambulating in an immobilizing boot. This paradigm provides a clinically implementable strategy to longitudinally monitor patient loading and activity while recovering from Achilles tendon injuries.

Patient-Reported Outcome Measures After Surgical Management of Unstable Lisfranc Injuries in Athletes.

Background: Athletes sustaining Lisfranc joint instability after a low-energy injury often undergo surgical fixation. Limited studies report validated patient-reported outcome measures (PROMs) for this specific patient population. Our purpose was to report PROMs of athletes experiencing instability after a low-energy Lisfranc injury and undergoing surgical fixation. Methods: Twenty-nine athletes (23 competitive, 6 recreational) sustained an unstable Lisfranc injury (14 acute, 15 chronic) and met our inclusion criteria. Injuries were classified as acute if surgically managed within 6 weeks. All athletes completed validated PROMs pre- and postoperatively. The cohort underwent various open reduction internal fixation methods. We evaluated outcomes with the Foot and Ankle Ability Measure (FAAM) activities of daily living (ADL) and sports subscales. Results: Fourteen of 29 (48%) athletes reported PROMs at ≥2 years with a median follow-up time of 44.5 months. Substantial improvement for both FAAM ADL (50% vs 93%; P < .001) and sports (14.1% vs 80%; P = .002) subscales were found, when comparing preoperative to postoperative scores at ≥2 years. Conclusion: This study provides outcomes information for the young athletic population that were treated operatively for low-energy Lisfranc injury with apparent joint instability. Based on the FAAM sports subscale, these patients on average improved between their 6-month evaluation and their final ≥2 years but still scored 80% of the possible 100%, which indicates continued but "slight" difficulty with lower extremity function. Level of Evidence: Level IV, case series.

Wearable sensor and machine learning estimate tendon load and walking speed during immobilizing boot ambulation.

The purpose of this study is to develop a wearable paradigm to accurately monitor Achilles tendon loading and walking speed using wearable sensors that reduce subject burden. Ten healthy adults walked in an immobilizing boot under various heel wedge conditions (30°, 5°, 0°) and walking speeds. Three-dimensional motion capture, ground reaction force, and 6-axis inertial measurement unit (IMU) signals were collected. We used a Least Absolute Shrinkage and Selection Operator (LASSO) regression to predict peak Achilles tendon load and walking speed. The effects of altering sensor parameters were also explored. Walking speed models (mean absolute percentage error (MAPE): 8.81 ± 4.29%) outperformed tendon load models (MAPE: 34.93 ± 26.3%). Models trained with subject-specific data performed better than models trained without subject-specific data. Removing the gyroscope, decreasing the sampling frequency, and using combinations of sensors did not change the usability of the models, having inconsequential effects on model performance. We developed a simple monitoring paradigm that uses LASSO regression and wearable sensors to accurately predict (MAPE ≤ 12.6%) Achilles tendon loading and walking speed while ambulating in an immobilizing boot. This paradigm provides a clinically implementable strategy to longitudinally monitor patient loading and activity while recovering from Achilles tendon injuries.

The Effects of Sociodemographic Factors on Baseline Patient-Reported Outcome Measures in Patients with Foot and Ankle Conditions.

BACKGROUND: Racial and ethnic care disparities persist within orthopaedics in the United States. This study aimed to deepen our understanding of which sociodemographic factors most impact patient-reported outcome measure (PROM) score variation and may explain racial and ethnic disparities in PROM scores. METHODS: We retrospectively reviewed baseline PROMIS (Patient-Reported Outcomes Measurement Information System) Global-Physical (PGP) and PROMIS Global-Mental (PGM) scores of 23,171 foot and ankle patients who completed the instrument from 2016 to 2021. A series of regression models was used to evaluate scores by race and ethnicity after adjusting in a stepwise fashion for household income, education level, primary language, Charlson Comorbidity Index (CCI), sex, and age. Full models were utilized to compare independent effects of predictors. RESULTS: For the PGP and PGM, adjusting for income, education level, and CCI reduced racial disparity by 61% and 54%, respectively, and adjusting for education level, language, and income reduced ethnic disparity by 67% and 65%, respectively. Full models revealed that an education level of high school or less and a severe CCI had the largest negative effects on scores. CONCLUSIONS: Education level, primary language, income, and CCI explained the majority (but not all) of the racial and ethnic disparities in our cohort. Among the explored factors, education level and CCI were predominant drivers of PROM score variation. LEVEL OF EVIDENCE: Prognostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Pre-Operative Bariatric Surgery Imparts An Increased Risk of Infection, Re-Admission and Operative Intervention Following Elective Instrumented Lumbar Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To evaluate the impact of bariatric surgery on patient outcomes following elective instrumented lumbar fusion. METHODS: A retrospective review of a prospectively collected database was performed. Patients who underwent a bariatric procedure prior to an elective instrumented lumbar fusion were evaluated. Lumbar procedures were performed at a large academic medical center from 1/1/2012 to 1/1/2018. The primary outcome was surgical site infection (SSI) requiring surgical debridement. Secondary outcomes were prolonged wound drainage requiring treatment, implant failure requiring revision, revision secondary to adjacent segment disease (ASD), and chronic pain states. A randomly selected, surgeon and comorbidity-matched group of 59 patients that underwent an elective lumbar fusion during that period was used as a control. Statistical analysis was performed using Student's two-way t-tests for continuous data, with significance defined as P < .05. RESULTS: Twenty-five patients were identified who underwent bariatric surgery prior to elective lumbar fusion. Mean follow-up was 2.4 ± 1.9 years in the bariatric group vs. 1.5 ± 1.3 years in the control group. Patients with a history of bariatric surgery had an increased incidence of SSI that required operative debridement, revision surgery due to ASD, and a higher incidence of chronic pain. Prolonged wound drainage and implant failure were equivalent between groups. CONCLUSION: In the present study, bariatric surgery prior to elective instrumented lumbar fusion was associated increased risk of surgical site infection, adjacent segment disease and chronic pain when compared to non-bariatric patients.

Environmental Sustainability in the Orthopaedic Operating Room.

Hotter global temperatures and increasingly variable climate patterns negatively affect human health, with a wide recognition that climate change is a major global health threat. Human activities, including those conducted in the orthopaedic operating room (OR), contribute to climate change by generating greenhouse gases that trap infrared radiation from the earth's surface. This review provides an overview of the environmental effect of the orthopaedic OR and efforts to address environmental sustainability in the OR. These concepts are presented with a particular focus on patient safety and cost savings because roll-out of these efforts must be conducted with a pragmatic and patient-centered focus. Orthopaedic surgeons have an opportunity to lead efforts to improve environmental sustainability in the OR and thus contribute to efforts to curb climate change.

Progressive Collapsing Foot Deformity: Should We Be Staging It Differently?

This article cursorily reviews the history of classification systems for pathologic flatfoot deformity in the adult and also critically reviews the recent introduction of a classification system intended to improve on the deficiencies of prior systems. The article concludes by offering suggestions for further work in evolving even more utilitarian systems for the staging and treatment of adult flatfoot disorder.

Use of Fondaparinux Following Elective Lumbar Spine Surgery Is Associated With a Reduction in Symptomatic Venous Thromboembolism.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To assess the impact of fondaparinux on venous thromboembolism (VTE) following elective lumbar spine surgery in high-risk patients. METHODS: Matched patient cohorts who did or did not receive inpatient fondaparinux starting postoperative day 2 following elective lumbar spine surgery were compared. All patients received 1 month of acetyl salicylic acid 325 mg following discharge. The primary outcome was a symptomatic DVT (deep vein thrombosis) or PE (pulmonary embolus) within 30 days of surgery. Secondary outcomes included prolonged wound drainage, epidural hematoma, and transfusion. RESULTS: A significantly higher number of DVTs were diagnosed in the group that did not receive inpatient VTE prophylaxis (3/102, 2.9%) compared with the fondaparinux group (0/275, 0%, P = .02). Increased wound drainage was seen in 18.5% of patients administered fondaparinux, compared with 25.5% of untreated patients (P = .15). Deep infections were equivalent (2.2% with fondaparinux vs 4.9% control, P = .18). No epidural hematomas were noted, and the number of transfusions after postoperative day 2 and 90-day return to operating room rates were equivalent. CONCLUSIONS: Patients receiving fondaparinux had lower rates of symptomatic DVT and PE and a favorable complication profile when compared with matched controls. The retrospective nature of this work limits the safety and efficacy claims that can be made about the use of fondaparinux to prevent VTE in elective lumbar spine surgery patients. Importantly, this work highlights the potential safety of this regimen, permitting future high-quality trials.

Cervical Spine Fractures: Who Really Needs CT Angiography?

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Compare a novel two-step algorithm for indicating a computed tomography angiography (CTA) in the setting of a cervical spine fracture with established gold standard criteria. SUMMARY OF BACKGROUND DATA: As CTA permits the rapid detection of blunt cerebrovascular injuries (BCVI), screening criteria for its use have broadened. However, more recent work warns of the potential for the overdiagnosis of BCVI, which must be considered with the adoption of broad criteria. METHODS: A novel two-step metric for indicating CTA screening was compared with the American College of Surgeons guidelines and the expanded Denver Criteria using patients who presented with cervical spine fractures to a tertiary-level 1 trauma center from January 1, 2012 to January 1, 2016. The ability for each metric to identify BCVI and posterior circulation strokes that occurred during this period was assessed. RESULTS: A total of 721 patients with cervical fractures were included, of whom 417 underwent CTAs (57.8%). Sixty-eight BCVIs and seven strokes were diagnosed in this cohort. All algorithms detected an equivalent number of BCVIs (52 with the novel metric, 54 with the ACS and Denver Criteria, P = 0.84) and strokes (7/7, 100% with the novel metric, 6/7, 85.7% with the ACS and Denver Criteria, P = 1.0). However, 63% fewer scans would have been needed with the proposed screening algorithm compared with the ACS or Denver Criteria (261/721, 36.2% of all patients with our criteria vs. 413/721, 57.3% with the ACS standard and 417/721, 57.8%) with the Denver Criteria, P < 0.0002 for each). CONCLUSION: A two-step criterion based on mechanism of injury and patient factors is a potentially useful guide for identifying patients at risk of BCVI and stroke after cervical spine fractures. Further prospective analyses are required prior to widespread clinical adoption. LEVEL OF EVIDENCE: 4.

Lesion Size Measured on MRI Does Not Accurately Reflect Arthroscopic Measurement in Talar Osteochondral Lesions.

BACKGROUND: Lesion size is a major determinant of treatment strategy for osteochondral lesions of the talus (OLTs). Although magnetic resonance imaging (MRI) is commonly used in the preoperative evaluation of OLTs, the reliability of the MRI measurement compared with the arthroscopic measurement is unknown. PURPOSE: To compare preoperative lesion size measured on MRI versus intraoperative lesion size measured during arthroscopy. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: We retrospectively reviewed a consecutive series of patients treated with bone marrow stimulation for OLTs. The diameter of the lesion was measured at its widest point in 2 planes, and MRI measurements were compared with those made during arthroscopy using a custom-made graduated probe. RESULTS: A total of 39 patients with 45 OLTs were analyzed. Mean ± SD area measurements on MRI were significantly greater than the equivalent arthroscopic measurements (42.2 ± 30.5 vs 28.6 ± 23.1 mm2, respectively; P = .03). Compared with the arthroscopic measurement, MRI overestimated OLT size in 53.3% (24/45) of ankles and underestimated OLT size in 24.4% (11/45). The mean MRI diameter measurement was significantly greater than the arthroscopic measurement in the coronal plane (MRI diameter vs arthroscopic measurement coronal plane, 6.1 ± 2.6 vs 4.9 ± 2.3 mm, P = .03; sagittal plane, 8.0 ± 3.6 vs 6.3 ± 3.6 mm, P = .05). Further, MRI overestimated coronal diameter in 48.9% (22/45) of ankles and underestimated in 26.7% (12/45) compared with the arthroscopic measurement. Similarly, sagittal plane MRI diameter measurements overestimated lesion size in 46.7% (21/45) of ankles and underestimated lesion size in 28.9% (13/45) compared with the arthroscopic findings. CONCLUSION: In a majority of lesions, MRI overestimated OLT area and diameter compared with arthroscopy. Surgeons should be aware of the discrepancies that can exist between MRI and arthroscopic measurements, as these data are important in making treatment decisions and educating patients.

"Post-Decompressive Neuropathy": New-Onset Post-Laminectomy Lower Extremity Neuropathic Pain Different from the Preoperative Complaint.

STUDY DESIGN: Level III retrospective cross-sectional study. PURPOSE: To define and characterize the presentation, symptom duration, and patient/surgical risk factors associated with 'postdecompressive neuropathy (PDN).' OVERVIEW OF LITERATURE: PDN is characterized by lower extremity radicular pain that is 'different' from pre-surgical radiculopathy or claudication pain. Although it is a common constellation of postoperative symptoms, PDN is incompletely characterized and poorly understood. We hypothesize that PDN is caused by an intraoperative neuropraxic event and may develop early (within 30 days following the procedure) or late (after 30 days following the procedure) within the postoperative period. METHODS: Patients who consented to undergo lumbar laminectomy with or without an instrumented fusion for degenerative lumbar spine disease were followed up prospectively from July 2013 to December 2014. Relevant data were extracted from the charts of the eligible patients. Patient demographics and surgical factors were identified. Patients completed postoperative questionnaires 3 weeks, 3 months, 6 months, and 1 year postoperatively. Questions were designed to characterize the postoperative pain that differed from preoperative pain. A diagnosis of PDN was established if the patient exhibited the following characteristics: pain different from preoperative pain, leg pain worse than back pain, a non-dermatomal pain pattern, and nocturnal pain that often disrupted sleep. A Visual Analog Scale was used to monitor the pain, and patients documented the effectiveness of the prescribed pain management modalities. Patients for whom more than one follow-up survey was missed were excluded from analysis. RESULTS: Of the 164 eligible patients, 118 (72.0%) completed at least one follow-up survey at each time interval. Of these eligible patients, 91 (77.1%) described symptoms consistent with PDN. Additionally, 75 patients (82.4%) described early-onset symptoms, whereas 16 reported symptoms consistent with late-onset PDN. Significantly more female patients reported PDN symptoms (87% vs. 69%, p=0.03). Patients with both early and late development of PDN described their leg pain as an intermittent, constant, burning, sharp/stabbing, or dull ache. Early PDN was categorized more commonly as a dull ache than late-onset PDN (60% vs. 31%, p=0.052); however, the difference did not reach statistical significance. Opioids were significantly more effective for patients with early-onset PDN than for those with late-onset PDN (85% vs. 44%, p=0.001). Gabapentin was most commonly prescribed to patients who cited no resolution of symptoms (70% vs. 31%, p=0.003). Time to symptom resolution ranged from within 1 month to 1 year. Patients' symptoms were considered unresolved if symptoms persisted for more than 1 year postoperatively. In total, 81% of the patients with earlyonset PDN reported complete symptom resolution 1 year postoperatively compared with 63% of patients with late-onset PDN (p=0.11). CONCLUSIONS: PDN is a discrete postoperative pain phenomenon that occurred in 77% of the patients who underwent lumbar laminectomy with or without instrumented fusion. Attention must be paid to the constellation and natural history of symptoms unique to PDN to effectively manage a self-limiting postoperative issue.

Rehabilitation and Return to Sports: Proceedings of the International Consensus Meeting on Cartilage Repair of the Ankle.

BACKGROUND: The evidence supporting best practice guidelines in the field of cartilage repair of the ankle are based on both low quality and low levels of evidence. Therefore, an international consensus group of experts was convened to collaboratively advance toward consensus opinions based on the best available evidence on key topics within cartilage repair of the ankle. The purpose of this article is to report the consensus statements on Rehabilitation and Return to Sports developed at the 2017 International Consensus Meeting on Cartilage Repair of the Ankle. METHODS: Seventy-five international experts in cartilage repair of the ankle representing 25 countries and 1 territory were convened and participated in a process based on the Delphi method of achieving consensus. Questions and statements were drafted within 11 working groups focusing on specific topics within cartilage repair of the ankle, after which a comprehensive literature review was performed and the available evidence for each statement was graded. Discussion and debate occurred in cases where statements were not agreed upon in unanimous fashion within the working groups. A final vote was then held, and the strength of consensus was characterized as follows: consensus, 51% to 74%; strong consensus, 75% to 99%; unanimous, 100%. RESULTS: A total of 9 statements on rehabilitation and return to sports reached consensus during the 2017 International Consensus Meeting on Cartilage Repair of the Ankle. All 9 statements reached strong consensus, with at least 86% agreement. CONCLUSIONS: The rehabilitation process for an ankle cartilage injury requires a multidisciplinary and comprehensive approach. This international consensus derived from leaders in the field will assist clinicians with rehabilitation and return to sports after treatment of a cartilage injury of the ankle.

Platelet-rich plasma increases transforming growth factor-beta1 expression at graft-host interface following autologous osteochondral transplantation in a rabbit model.

AIM: To explore the effect of platelet-rich plasma on protein expression patterns of transforming growth factor-beta1 (TGF-ß1) in cartilage following autologous osteochondral transplantation (AOT) in a rabbit knee cartilage defect model. METHODS: Twelve New Zealand white rabbits received bilateral AOT. In each rabbit, one knee was randomized to receive an autologous platelet rich plasma (PRP) injection and the contralateral knee received saline injection. Rabbits were euthanized at 3, 6 and 12 wk post-operatively. Articular cartilage sections were stained with TGF-ß1 antibody. Histological regions of interest (ROI) (left, right and center of the autologous grafts interfaces) were evaluated using MetaMorph. Percentage of chondrocytes positive for TGF-ß1 was then assessed. RESULTS: Percentage of chondrocytes positive for TGF-ß1 was higher in PRP treated knees for selected ROIs (left; P = 0.03, center; P = 0.05) compared to control and was also higher in the PRP group at each post-operative time point (P = 6.6 × 10(-4), 3.1 × 10(-4) and 7.3 × 10(-3) for 3, 6 and 12 wk, respectively). TGF-ß1 expression was higher in chondrocytes of PRP-treated knees (36% ± 29% vs 15% ± 18%) (P = 1.8 × 10(-6)) overall for each post-operative time point and ROI. CONCLUSION: Articular cartilage of rabbits treated with AOT and PRP exhibit increased TGF-ß1 expression compared to those treated with AOT and saline. Our findings suggest that adjunctive PRP may increase TGF-ß1 expression, which may play a role in the chondrogenic effect of PRP in vivo.