Femoral Contact Forces in the Anterior Cruciate Ligament Deficient Knee: A Robotic Study.

PURPOSE: To measure contact forces (CFs) at standardized locations representative of clinical articular cartilage defects on the medial and lateral femoral condyles during robotic tests with simulated weightbearing knee flexion. METHODS: Eleven human knees had 20-mm-diameter cylinders of native bone/cartilage cored from both femoral condyles at standardized locations, with each cylinder attached to a custom-built load cell that maintained the plug in its precise anatomic position. A robotic test system was used to flex the knee from 0° to 50° under 200-N tibiofemoral compression without and with a 2 Nm internal tibial torque, 5 Nm external tibial torque, and 45 N anterior tibial force (AF). CFs and knee kinematics were recorded before and after cutting the anterior cruciate ligament (ACL). RESULTS: ACL sectioning did not significantly increase medial or lateral CFs for any loading condition, with the exception of AF, in which increases in medial CF ranged from 38 N (at 15° flexion, P < .01) to 77 N (at 50° flexion, P < .002). Compared with the intact condition, ACL sectioning significantly increased anterior tibial translation by 12.33 mm (at 15° flexion, P < .001) and 17.4 mm (at 50° flexion, P < .001), and increased valgus rotation by 2.4° (at 15° flexion, P < .001) and 3.8° (at 50° flexion, P < .001). CONCLUSIONS: Our hypothesis that CF would increase after ACL section was confirmed for the AF test condition only, and only for the medial condyle beyond 10° flexion. With the ACL sectioned, it appeared that the increased CF was owing to the medial condyle riding up over the posterior tibial plateau resulting from the large anterior tibial displacements. CLINICAL RELEVANCE: Aside from our limited finding with AF, we concluded that CFs were generally unaffected by ACL section.

Demographic Trends and Complication Rates in Arthroscopic Elbow Surgery.

PURPOSE: To investigate demographic trends in elbow arthroscopy over time, as well as to query complication rates requiring reoperation associated with these procedures. METHODS: The Current Procedural Terminology (CPT) billing codes of patients undergoing elbow arthroscopy were searched using a national insurance database. From the years 2007 to 2011, over 20 million orthopaedic patient records were present in the database with an orthopaedic International Classification of Diseases, Ninth Revision diagnosis code or CPT code. Our search for procedures and the corresponding CPT codes for the elbow included diagnostic arthroscopy, loose body removal, synovectomy, and debridement. The type of procedure, date, gender, and region of the country were identified for each patient. In addition, the incidence of reoperation for infection, stiffness, and nerve injury was examined. RESULTS: There was a significant increase in arthroscopic elbow procedures over the study period. Male patients accounted for 71% of patients undergoing these procedures. Of the elbow arthroscopy patients, 22% were aged younger than 20 years, 25% were aged 20 to 39 years, 47% were aged 40 to 59 years, and 6% were aged 60 years or older. Other than synovectomy, there were regional variations in the incidence of each procedure type. The overall rate of reoperation was 2.2%, with specific rates of 0.26% for infection, 0.63% for stiffness, and 1.26% for nerve injury. It should be noted that because only the complications requiring reoperation are recorded in the database, these numbers are lower than the overall complication rate. CONCLUSIONS: Overall, the incidence of elbow arthroscopy in this patient population is relatively low and appears to be increasing slightly over time. In the database used in this study, elbow arthroscopy procedures were most commonly performed in male patients and in patients aged 40 to 59 years, with regional variation in the incidence of the different procedures. Furthermore, the rate of complications requiring reoperation was low, with a nerve operation being the most common reoperation performed. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Utilization and Costs of Postoperative Physical Therapy After Rotator Cuff Repair: A Comparison of Privately Insured and Medicare Patients.

PURPOSE: To evaluate the utilization and charges related to physical therapy (PT) after rotator cuff repair in privately insured and Medicare patients and between arthroscopic and open/mini-open repair techniques. METHODS: The PearlDiver insurance database was queried for patients receiving postoperative PT using Current Procedural Terminology codes. Data were available from 2007 to 2011 for United Healthcare and from 2005 to 2011 for Medicare patients. Patients undergoing arthroscopic (CPT 29827) or open/mini-open approaches (CPT 23410, 23412, 23420) were identified in both populations. Utilization was determined by both the percentage of patients with at least one postoperative PT-related code and the average number of encounters per patient. Per-patient average charge was determined by dividing total charges within the billing period by the patient total. RESULTS: A total of 365,891 patients undergoing rotator cuff repair were identified. There was an increase in the number of arthroscopic repairs (+29.1%, P = .027, United Healthcare; +78.9%, P < .001, Medicare) and a decrease in the number of open/mini-open repairs (-18.2%, P = .038, United Healthcare; -18.2%, P < .001, Medicare) across the study period. At 6 months postoperatively, PT utilization was greater in the United Healthcare groups (82.9% arthroscopic, 81.0% open/mini-open) than in the Medicare groups (41.8% arthroscopic, 43.2% open/mini-open). Utilization-weighted per-patient average charge was comparable among all 4 groups, with slightly higher charges in the United Healthcare groups ($3,376 arthroscopic, $3,251 open/mini-open) compared with the Medicare groups ($2,940 arthroscopic, $2,807 open/mini-open). The United Healthcare groups had a greater number of utilization-weighted billed encounters (36.1 for open/mini-open, 9.5 for arthroscopic) than their Medicare counterparts (12.8 open/mini-open, 16.7 arthroscopic). CONCLUSIONS: Utilization of PT after rotator cuff repair is substantially higher in privately insured than in Medicare patients. Utilization rates appear to be comparable between surgical approaches. Per-patient costs were comparable irrespective of surgical approach and insurance modality. LEVEL OF EVIDENCE: Level IV, economic.

Measurements of tibial rotation during a simulated pivot shift manoeuvre using a gyroscopic sensor.

PURPOSE: The pivot shift has been correlated with patient-reported outcomes and knee function following ACL injury and reconstruction. Tibial rotation has been recognized as an important component to the pivot shift motion path. However, few methodologies exist to quantify tibial rotation in the clinical setting. The purpose of this study was to validate the use of a wireless gyroscopic sensor to measure axial rotation of the tibia during a manually simulated pivot shift manoeuvre in cadaveric specimens. We hypothesized that integrated gyroscopic measurements of tibial rotation velocity (tibial rotation) would be highly correlated with tibial rotations simultaneously recorded with a rotary potentiometer during a simulated pivot shift motion under intact and ACL-deficient conditions. METHODS: Gyroscopic measurements of rotational velocity were integrated and calibrated to a known arc of rotation. The gyroscope was mounted on the distal tibia with its axis aligned to the tibial shaft. Ten simulations of a pivot shift motion pathway were performed on nine cadaveric knees under intact and ACL-deficient conditions. Logistic regression was used to compare gyroscopic and potentiometer measurements of tibial rotation for both test conditions. RESULTS: Gyroscopic measurements of maximum external tibial rotation during the simulated pivot shift motion pathway were strongly correlated with potentiometer measurements of external tibial rotation in both the intact and ACL-deficient states (R (2) = 0.984). CONCLUSION: The gyroscope evaluated in this cadaveric study was capable of accurately recording tibial rotation during a simulated pivot shift motion pathway.

Demographic trends in arthroscopic and open biceps tenodesis across the United States.

BACKGROUND: The purpose of this study was to evaluate trends in procedures and to report on demographic data of patients undergoing arthroscopic vs. open biceps tenodesis. METHODS: A retrospective review of a commercially available database (PearlDiver) was conducted to identify cases of arthroscopic and open biceps tenodesis performed between 2007 and 2011 with concurrent diagnoses of commonly associated shoulder disorders. Each record provided the patient's age, gender, and region within the United States, and statistical significance was determined with respect to each of these demographics. RESULTS: There were 9011 patients who underwent arthroscopic biceps tenodesis and 11,678 patients who underwent open biceps tenodesis between 2007 and 2011. The number of biceps tenodesis cases increased from 2007 to 2011 (2047 to 5832; P = .015). Both arthroscopic and open biceps tenodesis procedures were performed most commonly in the 30- to 59-year-old age group (76.3% and 76.1%; P < .00001). Men underwent arthroscopic or open biceps tenodesis more commonly than women did (66.1% and 71.9%; P < .00001). Rates of both open and arthroscopic biceps tenodesis varied significantly among the Midwest, South, Northeast, and West regions (P = .009; P = .007); 49.8% of arthroscopic and 44.6% of open biceps tenodesis cases were associated with rotator cuff tears, whereas 14.4% of arthroscopic and 16.2% of open cases were associated with biceps tendon disorders. CONCLUSION: Both arthroscopic and open biceps tenodesis cases increased annually from 2007 to 2011. The majority of biceps tenodesis cases were performed in men aged 30 to 59 years, and the South had the highest overall number of cases. Further studies are required to evaluate the efficacy of these procedures with and without concomitant pathologic processes.

Anatomic Factors that May Predispose Female Athletes to Anterior Cruciate Ligament Injury.

Female athletes are 2 to 10 times more likely to injure their anterior cruciate ligaments (ACL) than male athletes. There has been greater recognition of this gender discrepancy because female participation in competitive athletics has increased. Previous investigators have divided risk factors into hormonal, neuromuscular response, and anatomic subgroups. Gender variation within these groups may help explain the higher incidence of ACL injury in women. The purpose of this article is to review research examining female-specific anatomy that may predispose women to ACL injury. Specifically, we discuss how women may have increased tibial and meniscal slopes, narrower femoral notches, and smaller ACL, which may place the ACL at risk from injury. These anatomic factors, combined with other female-specific risk factors, may help physicians and researchers better understand why women appear to be more prone to ACL injury.

Vascular and nerve injury after knee dislocation: a systematic review.

BACKGROUND: Vascular injury is a devastating complication of acute knee dislocation. However, there are wide discrepancies in the reported frequency of vascular injury after knee dislocations, as well as important differences among approaches for diagnosis of this potentially limb-threatening problem. QUESTIONS/PURPOSES: We determined (1) the frequency of vascular and neurologic injury after knee dislocation and whether it varied by the type of knee dislocation, (2) the frequency with which surgical intervention was performed for vascular injury in this setting, and (3) the frequency with which each imaging modality was used to detect vascular injury. METHODS: We searched the MEDLINE(®) literature database for studies in English that examined the clinical sequelae and diagnostic evaluation after knee dislocation. Vascular and nerve injury incidence after knee dislocation, surgical repair rate within vascular injury, and amputation rate after vascular injury were used to perform a meta-analysis. Other measures such as diagnostic modality used and the vessel injured after knee dislocation were also evaluated. RESULTS: We identified 862 patients with knee dislocations, of whom 171 sustained vascular injury, yielding a weighted frequency of 18%. The frequency of nerve injuries after knee dislocation was 25% (75 of 272). We found that 80% (134 of 160) of vascular injuries underwent repair, and 12% (22 of 134) of vascular injuries resulted in amputation. The Schenck and Kennedy knee dislocation classifications with the highest vascular injury prevalence were observed in knees that involved the ACL, PCL, and medial collateral liagment (KDIIIL) (32%) and posterior dislocation (25%), respectively. Selective angiography was the most frequently used diagnostic modality (61%, 14 of 23), followed by nonselective angiography and duplex ultrasonography (22%, five of 23), ankle-brachial index (17%, four of 23), and MR angiography (9%, two of 23). CONCLUSIONS: This review enhances our understanding of the frequency of vascular injury and repair, amputation, and nerve injuries after knee dislocation. It also illustrates the lack of consensus among practitioners regarding the diagnostic and treatment algorithm for vascular injury. After pooling existing data on this topic, no outcomes-driven conclusions could be drawn regarding the ideal diagnostic modality or indications for surgical repair. In light of these findings and the morbidity associated with a missed diagnosis, clinicians should err on the side of caution in ruling out arterial injury.

The changing demographics of knee dislocation: a retrospective database review.

BACKGROUND: Knee dislocations are uncommon but devastating orthopaedic injuries. Little is known about their frequency and the types of patients who are affected. QUESTIONS/PURPOSES: Using a large national insurance database, we determined (1) the incidence of knee dislocation in patients with orthopaedic injuries and examined the incidence as a function of (2) year of diagnosis, (3) dislocation type (open versus closed, direction), and (4) patient demographic factors (sex, age). METHODS: We searched the PearlDiver database, a national database of private insurance records consisting of 11 million patients with orthopaedic diagnoses, using diagnosis (ICD-9-CM) codes for knee dislocation between the years 2004 and 2009. The PearlDiver database does not include Medicare, Medicaid, or uninsured patients. Patients were stratified by age, sex, and year of diagnosis. Incidence was defined as the number of dislocation events per 100 patient-years. RESULTS: We identified 8050 dislocations, representing an incidence of 0.072 events per 100 patient-years between 2004 and 2009. Annual dislocation incidence did not increase during the 6-year study period. Of the 8050 dislocations, 1333 (17%) were open and 6717 (83%) were closed, representing an incidence of 0.060 per 100 for closed dislocations and 0.012 per 100 for open dislocations. The most common direction of dislocation was unspecified or other (65%), followed by anterior (13%), lateral (11%), posterior (6%), and medial (5%). Of the patients sustaining dislocations, 4172 (52%) were female and 3878 (48%) were male. Males displayed an increased risk of knee dislocation compared to females (odds ratio = 1.09). The mean patient age was 35 years, and patient age was inversely correlated to the incidence of knee dislocation (10-year odds ratio = 0.77). CONCLUSIONS: Our data suggest that knee dislocation might represent a significantly larger burden among orthopaedic injuries than previously thought. The finding that males and females have a nearly equal risk of knee dislocation enhances the diagnosing physician's clinical suspicion of this injury. Future large prospective studies analyzing the various causes of knee dislocation could provide insight into the changing demographics of this injury. LEVEL OF EVIDENCE: Level IV, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

What is the frequency of vascular injury after knee dislocation?

BACKGROUND: Vascular injury secondary to an acute knee dislocation is a known complication. However, there exist wide discrepancies in the reported rate of vascular injury in this setting. QUESTIONS/PURPOSES: Using a large private insurance database, we determined the frequency of vascular injury in knee dislocations across year of diagnosis, age, sex, and US geographic region and the proportion of these injuries requiring surgical repair. METHODS: The PearlDiver database, which contains records from 11 million orthopaedic patients, was searched using ICD-9 diagnostic codes for all knee dislocation events from 2004 to 2009. Within this subset, we identified which knee dislocations had an associated vascular injury ICD-9 code. Patients were stratified by year of diagnosis, age, sex, and US geographic region, and Current Procedural Terminology codes were used to identify the subset of patients with vascular injury requiring surgical repair. Differences in frequency across demographic groups and over time were analyzed with Poisson regression analysis. RESULTS: Among the 8050 limbs with knee dislocation identified over the study period, 267 had a concomitant vascular injury for an overall frequency of 3.3%. Males were found to have an increased risk of vascular injury compared to females (odds ratio = 2.59, p < 0.001). Additionally, patients aged 20 to 39 years had a higher risk of vascular injury when compared to those aged 0 to 19 years (odds ratio = 1.93, p = 0.001), 40 to 59 years (odds ratio = 1.57, p = 0.014), and 60 years or older (odds ratio = 2.81, p = 0.036). There were no differences in vascular injury frequency across US geographic regions or diagnosis year. Thirty-four of the 267 cases of vascular injury (13%) underwent surgical treatment. CONCLUSIONS: This is the largest study, to our knowledge, that analyzes the proportion of knee dislocations that result in vascular injury. Our data suggest that there is a lower frequency of vascular injury associated with knee dislocation and a lower proportion of vascular injuries undergoing surgical treatment than previously reported. These findings may support a more selective angiography protocol to screen for vascular injury, rather than performing this invasive diagnostic test on all knee dislocations, as has been done historically. Future large-scale and prospective studies should analyze factors that may predispose to vascular injuries after knee dislocation and determine which patients should be screened for vascular injury after knee dislocation. LEVEL OF EVIDENCE: Level IV, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

Use of a gyroscope sensor to quantify tibial motions during a pivot shift test.

PURPOSE: The purpose of this preliminary study was to evaluate the use of a gyroscope sensor to record rotations of the tibia about its long axis during a clinical pivot shift examination. METHODS: Ten patients with a unilateral ACL injury were tested under anaesthesia prior to surgery. Each ankle was placed in neutral position, wrapped and stabilized with athletic tape, and a small aluminium plate was taped to the bottom of the foot. A data recovery module was attached to the bottom of each plate using a swivel bracket that allowed alignment of the gyro axis with the long axis of the tibia. The module contained a triaxial gyroscope, battery and circuitry for wireless data broadcast to a laptop computer. Ten pivot shift tests were performed on both knees, and the surgeon's clinical grading of the pivot shift was noted for each limb. Mean values (10 trials) of peak tibial rotational velocity and integrated tibial rotation were compared between knees for each patient during the pivot shift reduction event (external tibial rotation during knee flexion). RESULTS: Five patients (50%) had significantly greater tibial rotation in their injured knee, four showed no difference between knees, and one had significantly greater rotation in the normal knee (p < 0.05). Seven patients (70%) showed greater peak rotational velocity in their injured knee, and three had no difference between the knees (p < 0.05). Correlations of rotation and rotational velocity with clinical pivot shift grade were weak (r2 = 0.09 and 0.19, respectively). CONCLUSIONS: Foot gyroscope measurements did not correctly identify the injured limb in all patients. Peak rotational velocity during the reduction event was a better indicator of ACL deficiency than the integrated rotation. If this technology is to be more useful clinically, gyroscope data may have to be combined with accelerometer data, perhaps with sensors mounted on both the tibia and femur. LEVEL OF EVIDENCE: Diagnostic case-control study, Level III.

Trends in the surgical treatment of articular cartilage defects of the knee in the United States.

PURPOSE: The purpose of this study was to evaluate trends in surgical treatment of articular cartilage defects of the knee in the United States. METHODS: The current procedural terminology (CPT) billing codes of patients undergoing articular cartilage procedures of the knee were searched using the PearlDiver Patient Record Database, a national database of insurance billing records. The CPT codes for chondroplasty, microfracture, osteochondral autograft, osteochondral allograft, and autologous chondrocyte implantation (ACI) were searched. RESULTS: A total of 163,448 articular cartilage procedures of the knee were identified over a 6-year period. Microfracture and chondroplasty accounted for over 98% of cases. There was no significant change in the incidence of cartilage procedures noted from 2004 (1.27 cases per 10,000 patients) to 2009 (1.53 cases per 10,000 patients) (p = 0.06). All procedures were performed more commonly in males (p < 0.001). This gender difference was smallest in patients undergoing chondroplasty (51 % males and 49% females) and greatest for open osteochondral allograft (61% males and 39% females). Chondroplasty and microfracture were most commonly performed in patients aged 40-59, while all other procedures were performed most frequently in patients <40 years old (p < 0.001). CONCLUSIONS: Articular cartilage lesions of the knee are most commonly treated with microfracture or chondroplasty in the United States. Chondroplasty and microfracture were most often performed in middle-aged patients, whereas osteochondral autograft, allograft, and ACI were performed in younger patients, and more frequently in males. LEVEL OF EVIDENCE: Cross-sectional study, Level IV.

A Robotic Clamped-Kinematic System to Study Knee Ligament Injury.

Knee ligament injury is among the most common sports injuries and is associated with long recovery periods and low return-to-sport rates. Unfortunately, the mechanics of ligament injury are difficult to study in vivo, and computational studies provide limited insight. The objective of this study was to implement and validate a robotic system capable of reproducing natural six degree-of-freedom clamped-kinematic trajectories on human cadaver knees (meaning that positions and orientations are rigidly controlled and resultant loads are measured). To accomplish this, we leveraged the field's recent access to high-fidelity bone kinematics from dynamic biplanar radiography (DBR), and implemented these kinematics in a coordinate frame built around the knee's natural flexion-extension axis. We assessed our system's capabilities in the context of ACL injury, by moving seven cadaveric knee specimens through kinematics derived from walking, running, drop jump, and ACL injury. We then used robotically simulated clinical stability tests to evaluate the hypothesis that knee stability would be only reduced by the motions intended to injure the knee. Our results show that the structural integrity of the knee was not compromised by non-injurious motions, while the injury motion produced a clinically relevant ACL injury with characteristic anterior and valgus instability. We also demonstrated that our robotic system can provide direct measurements of reaction loads during a variety of motions, and facilitate gross evaluation of ligament failure mechanisms. Clamped-kinematic robotic evaluation of cadaver knees has the potential to deepen understanding of the mechanics of knee ligament injury.

Incidence of postoperative infections requiring reoperation after arthroscopic knee surgery.

PURPOSE: The purposes of this study were to determine the incidence of infection requiring reoperation after arthroscopic knee surgery during a 6-year period and to compare infection rates across different age groups, genders, geographic regions of the United States, and Current Procedural Terminology (CPT) codes through a retrospective review of a large insurance company database. METHODS: A retrospective review of an insurance company database was performed for all knee arthroscopies performed in the United States from 2004 to 2009. The database was first queried for all knee arthroscopies, and the number of those cases requiring additional surgery for infection within 30 days was determined to calculate the incidence of infection. The incidence was stratified by gender, age group, region within the United States, and CPT code. A separate analysis for procedures using allografts was also performed. RESULTS: A total of 432,038 arthroscopic surgeries were performed, and the number of infections requiring drainage was 638, for an overall incidence of infection from 2004 to 2009 of 0.15%. Among adults, men were affected almost twice as often as women (P < .001), and among children, boys were affected almost 3 times as often as girls (P < .001). A decreasing incidence was noted in patients 60 years or older between 2004 and 2009 (P = .01). Overall, the incidence did not significantly vary by age, region, or CPT codes that specified the implantation of allograft tissue. Compared with diagnostic arthroscopy, the relative risk of infection was higher for CPT-29889 (posterior cruciate ligament reconstruction). CONCLUSIONS: The incidence of infection requiring reoperation after knee arthroscopy from 2004 to 2009 was 0.15%. The incidence was higher among male patients in both the adult and pediatric populations. The incidence of infection decreased from 2004 to 2009 in patients 60 years or older. Among adult patients, the incidence did not vary by age, by region, or by CPT codes that involved implantation of allografts. LEVEL OF EVIDENCE: Level IV, cross-sectional study.

The costs associated with the evaluation of rotator cuff tears before surgical repair.

BACKGROUND: Patients undergoing rotator cuff repair typically have a diagnostic evaluation and trial of nonoperative therapy before surgery. Recent studies have evaluated the cost-effectiveness of surgery, but none have attempted to estimate the costs associated with the preoperative evaluation. This study used available data to examine major expenditures during the preoperative period. MATERIALS AND METHODS: We conducted a search using an insurance company database to identify patients undergoing rotator cuff repair from 2004 to 2009. Patients were identified by the common Current Procedural Terminology codes for rotator cuff repair. The associated charge codes for the 90-day period before surgery were categorized as outpatient physician visits, diagnostic imaging studies, injections, physical therapy, laboratory and other preoperative studies, prior surgeries, and miscellaneous. The frequency of each code and the associated charges were noted. RESULTS: In total, 92,688 patients were identified in the study period. A total of $161,993,100 was charged during the preoperative period, for an average of $1,748 per patient. Diagnostic imaging charges totaled $104,510,646 (65%); injections, $5,145,227 (3%); outpatient visits, $29,723,751 (18%); physical therapy, $13,844,270 (8.5%); preoperative studies, $6,792,245 (4.2%); and miscellaneous, $1,164,688 (<1%). CONCLUSIONS: The costs for preoperative evaluation of rotator cuff tears are substantial, and the majority of the costs are associated with magnetic resonance imaging. To help reduce costs, future studies should attempt to identify the factors that predict which patients might not respond to nonoperative management and might benefit from early surgical intervention. In addition, magnetic resonance imaging should perhaps be reserved for patients in whom the diagnosis cannot be achieved by other modalities.

Syndesmosis fixation using dual 3.5 mm and 4.5 mm screws with tricortical and quadricortical purchase: a biomechanical study.

BACKGROUND: Grade 3 syndesmosis (high ankle) sprains of the ankle are frequently treated using screws that fix the distal fibula to the tibia. We hypothesized that forces acting on the distal fibula and displacements of the distal fibula relative to the tibia recorded during simulated ankle loading tests would be significantly affected by syndesmosis screw size and the number of engaged tibial cortices. METHODS: Distal fibular forces and displacements were measured after cutting the distal inferior tibiofibular ligaments and fixing the distal fibula to the distal fibula with 2 syndesmosis screws. Screws of 3.5 mm and 4.5 mm were applied with tricortical and quadricortical purchase. RESULTS: There were no significant differences in distal fibular forces or displacements between any combination of screw size and cortical purchase tested. The highest mean fibular force recorded in the study (110.2 N) occurred when 10 N-m of external foot torque was applied to a dorsiflexed ankle loaded with 1000 N axial weight-bearing force. For ankle dorsiflexion and external foot torque tests, the distal fibula always displaced posteriorly with respect to the tibia. Mean displacements of the fibula from 1000 N applied axial weight-bearing force (maximum 0.15 mm) and from 10 N-m of forced foot dorsiflexion (maximum 0.43 mm) were considerably less than those from 10 N-m external foot torque (1.7 mm to 2.7 mm). CONCLUSIONS: Screw size and the number of engaged tibial cortices had no significant effect on mechanical stability of the distal fibula during these tests. Application of external foot torque (internal tibial torque) to a weight-bearing ankle produced the greatest bending displacements of the screws, and should be avoided during rehabilitation to reduce the possibility of screw breakage. CLINICAL RELEVANCE: In terms of mechanical stability, surgeons may have considerable flexibility with regard to screw fixation of high ankle sprains.

Force and displacement measurements of the distal fibula during simulated ankle loading tests for high ankle sprains.

BACKGROUND: Syndesmosis (high ankle) sprains produce disruption of the distal tibiofibular ligaments. Forces on the distal fibula that produce these injuries are unknown. METHODS: Twenty-seven fresh-frozen lower extremities were used for this study. A load cell recorded forces acting on the distal fibula from forced ankle dorsiflexion and applied external foot torque; medial-lateral and anterior-posterior displacements of the distal fibula were recorded. Fibular forces and axial displacements were also recorded with applied axial force. RESULTS: During forced ankle dorsiflexion and external foot torque tests, the distal fibula always displaced posteriorly with respect to the tibia with no measurable medial-lateral displacement. With 10 Nm dorsiflexion moment, cutting the tibiofibular ligaments approximately doubled fibular force and displacement values. Cutting the tibiofibular ligaments significantly increased fibular displacement from applied external foot torque. Fibular forces and axial displacements from applied axial weight-bearing force were highest with the foot dorsiflexed. The highest mean fibular force in the study (271.9 N) occurred with 10 Nm external foot torque applied to a dorsiflexed foot under 1000 N axial force. CONCLUSIONS: Two important modes of loading that could produce high ankle sprains were identified: forced ankle dorsiflexion and external foot torque applied to a dorsiflexed ankle loaded with axial force. The distal tibiofibular ligaments restrained fibular displacement during these tests. CLINICAL RELEVANCE: Residual mortise widening observed at surgery may be the result of tibiofibular ligament injuries caused by posterior displacement of the fibula. Therefore, a syndesmosis screw used to fix the fibula would be subjected to posterior bending forces from these loading modes. Ankle bracing to prevent extreme ankle dorsiflexion during rehabilitation may be advisable to prevent excessive fibular motions that could affect syndesmosis healing.

Changes in knee kinematics from applied external Tibial torque: Implications for stabilizing an anterior cruciate ligament deficient knee.

BACKGROUND: Changes in knee kinematics from internal tibial torque under tibiofemoral compression force have been studied, but the potentially stabilizing effects of external tibial torque have not been reported. We hypothesized that for a given knee flexion angle, 1) external torque would significantly reduce anterior tibial translation, internal tibial rotation, and valgus tibial rotation before and after sectioning the anterior cruciate ligament and 2) changes in kinematics from applied external torque would be significantly greater with the cruciate cut. METHODS: A robotic test system was used to flex intact human knees continuously from 0° to 50° under 200 N compression, without and with 5 Nm external torque. Tests were repeated after cruciate section. FINDINGS: With the cruciate intact, external torque had no significant effect on anterior translation, and significantly reduced internal and valgus rotations at all flexion angles. With the cruciate cut, external torque significantly reduced anterior translation beyond 25° flexion, significantly reduced internal rotation at all flexion angles, and significantly reduced valgus rotation beyond 15° flexion. Although external torque had no significant effect on anterior translation with the ACL intact, external torque produced relatively large decreases in anterior translation with the cruciate sectioned (-11.6 mm at 50° flexion). Reductions in valgus rotation from applied external torque were significantly greater for cruciate deficient knees beyond 25° flexion. INTERPRETATION: We conclude that external tibial torque may be important for controlling the abnormal kinematics associated with an anterior cruciate ligament deficient knee, and possibly help stabilize the knee during in vivo activities.

Surveillance testing for SARS-COV-2 infection in an asymptomatic athlete population: a prospective cohort study with 123 362 tests and 23 463 paired RT-PCR/antigen samples.

OBJECTIVE: To assess the diagnostic accuracy of antigen compared with reverse transcriptase (RT)-PCR testing in an asymptomatic athlete screening programme and to monitor infection in college athletes. METHODS: Quidel Sofia-2 SARS-CoV-2 Antigen Tests were performed daily before sports participation for football, basketball, wrestling and water polo from 29 September 2020 to 28 February 2021. Paired RT-PCR and antigen tests were performed at least once a week. Positive antigen tests were confirmed with RT-PCR. RESULTS: 81 175 antigen and 42 187 RT-PCR tests were performed, including 23 462 weekly paired antigen/RT-PCR screening tests in 1931 athletes. One hundred and seventy-two athletes had a positive screening RT-PCR (0.4%), of which 83 (48%) occurred on paired testing days. The sensitivity of antigen tests varied with the frequency of RT-PCR testing and prevalence of COVID-19. The sensitivity of antigen testing was 35.7% (95% CI: 17% to 60%) and specificity 99.8% (95% CI: 99.7% to 99.9%) with once-a-week RT-PCR testing after adjusting for school prevalence. Daily antigen testing was similar to RT-PCR testing two to three times a week in identifying infection. Antigen testing identified infection before the next scheduled PCR on 89 occasions and resulted in 234 days where potentially infectious athletes were isolated before they would have been isolated with RT-PCR testing alone. Two athletic-related outbreaks occurred; 86% of total infections were community acquired. CONCLUSION: Antigen testing has high specificity with a short turnaround time but is not as sensitive as RT-PCR. Daily antigen testing or RT-PCR testing two to three times a week is similar. There are benefits and drawbacks to each testing approach.

Aged Mice Demonstrate Greater Muscle Degeneration of Chronically Injured Rotator Cuff.

Massive tears of the rotator cuff (RC) are often associated with progressive and irreversible muscle degeneration due to fibrosis, fatty infiltration, and muscle atrophy. RC tears are common in individuals older than 60 years and the repair of these tears is amongst the most prevalent of orthopedic procedures. However, most current models of this injury are established in young animals, which may not accurately recapitulate the clinical condition. In this study, we used a murine model of massive RC tears to evaluate age-related muscle degeneration following chronic injury. The expression of the fibro-adipogenic genes encoding collagen type III and leptin was higher in aged RC compared with matched injured young tissue at 2 weeks post-injury, and development of fibrosis was accelerated in aged mice within 5 days post-injury. Furthermore, the synthesis of collagens type I and III and fat tissue accumulation were significantly higher in injured RCs of aged mice. Similar frequency of fibro-adipogenic PDGFRß+ PDGFRα+ progenitor cells was measured in non-injured RC of aged and young mice, but PDGFRß+ PDGFRα+ cells contributed to significantly larger fibrotic lesions in aged RCs within 2 weeks post-injury, implying a more robust fibrotic environment in the aged injured muscle. Altogether, these findings demonstrate age-dependent differences in RC response to chronic injury with a more profound fibro-adipogenic change in aged muscles. Clinically, cell therapies for muscular pathologies should not only consider the cell type being transplanted but also the recipient milieu into which these cells are seeded. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:320-328, 2020.

Posterior cruciate ligament biomechanics and options for surgical treatment.

Treatment algorithms for posterior cruciate ligament (PCL) injury have evolved over the past two decades as the natural history of these injuries has become clearer. Whether they are isolated injuries or occur with other ligament trauma, PCL ruptures substantially alter knee kinematics. Because of the effects of PCL injury and the less than optimal results after nonsurgical treatment, new surgical techniques have been developed. Several surgical techniques currently are available for reconstruction of the PCL. Most recent reports suggest that the tibial inlay technique is the best choice for restoring posterior tibial stability. Tibial inlay PCL reconstructions can be performed through both open and arthroscopic approaches. Crucial to the outcome of these procedures is detecting all injuries to the secondary restraints, especially the posterolateral corner. Failure to recognize and treat these deficits can compromise the results of PCL reconstruction, emphasizing the need for a detailed, meticulous physical examination when PCL injuries are suspected.