Pectoralis Major Injuries in the National Football League.

BACKGROUND: Pectoralis major (PM) injuries are rare, primarily occurring in males during athletic activity. In the current literature, these injuries have not been well described in National Football League (NFL) athletes. HYPOTHESIS: The incidence of PM injuries will be low in NFL athletes, with athletes missing significantly more time after injuries requiring operative management. STUDY DESIGN: Cohort study. LEVEL OF EVIDENCE: Level 4. METHODS: All documented PM injuries were retrospectively analyzed using the NFL Injury Surveillance System over a 15-season period. The data were analyzed by season, session, position, activity, and contact type at the time of injury. Additionally, the incidence, treatment, and days missed as a result of injury were assessed. RESULTS: Over 15 consecutive seasons, there were a total of 211 PM injuries. Of these injuries, 132 were classified as strains and 79 as ruptures. The incidence of strains was 0.41 per 10,000 athlete-exposures, compared with 0.25 per 10,0000 athlete-exposures for ruptures (P < 0.01). Players with PM ruptures treated operatively missed significantly more days than players treated nonoperatively (146.7 ± 55.0 vs 77.2 ± 72.9; P < 0.01). CONCLUSION: NFL athletes miss significantly more time after operative compared with nonoperative management of PM ruptures. CLINICAL RELEVANCE: PM injuries are rare, with the current literature lacking description of these injuries in NFL athletes. The paucity of data limits physicians from providing adequate counseling and expectations for athletes with this injury. This research represents the largest study assessing PM injuries in NFL athletes.

The negative impact of anterior cruciate ligament reconstruction in professional male footballers.

BACKGROUND: Soccer is one of the most common international sports in which ACL injuries occur, with previous studies reporting high return-to-play rates following ACL reconstruction (ACLR). Return-to-play analysis fails to take into consideration how effective a player remains once returning to competition. The aims of this study are to provide a large-scale international analysis of return-to-play and player performance statistics among professional soccer athletes following ACLR. METHODS: Using publicly available sources, professional soccer athletes who have undergone ACLR between the 1996 and 2015 seasons were identified. Player metrics including statistical performance, recovery time, and return-to-play rates were analyzed both before and after reconstruction. Furthermore, player performance statistics during each of three consecutive seasons post-ACLR were compared. RESULTS: A total of 176 athletes who underwent ACLR were included in this study. The return-to-play rate was 93.2% (164 athletes). Cumulative post-surgical statistical analysis of ACLR players demonstrated fewer games/season, minutes/season, minutes/game, goals/season, and more fouls/season following ACLR (p < 0.04). Analysis of player performance statistics suggests that athletes do not return to their baseline number of games/season and minutes/game until two and three seasons post-ACLR, respectively. At three seasons post-ACLR, athletes are still starting fewer games/season and scoring fewer goals/90 min (p < 0.04). CONCLUSION: Return-to-play rate is high following ACLR; however, athletes exhibit poorer statistical performance, especially in the first few seasons upon return. Our data shows that athletes continue to start fewer games/season and score fewer goals/90 min at three seasons post-ACLR.

Superior Labrum Anterior-Posterior Tears in the National Football League.

BACKGROUND: Shoulder disorders are common in football players, with up to 50% of National Football League (NFL) recruits reporting a history of shoulder injuries. Superior labrum anterior-posterior (SLAP) tears are an entity with well-described detrimental effects on return to play in overhead-throwing athletes but with minimal data in contact athletes. PURPOSE: To identify the incidence, predisposing factors, and effect of SLAP tears in NFL athletes and prospects as well as the treatment patterns of NFL team physicians. STUDY DESIGN: Descriptive epidemiology study. METHODS: This study was a comprehensive analysis of SLAP tears in elite football players using a dual approach: (1) SLAP injuries recorded in the NFL Injury Surveillance System from 2000 to 2014 were evaluated by player position, type of play, days/games lost, and surgical intervention; (2) NFL Scouting Combine athletes from 2003 to 2011 with prior SLAP repair were evaluated for draft success, and drafted athletes were compared with matched controls for career length and performance scores. RESULTS: SLAP tears represented a small portion (3.1%) of shoulder injuries in NFL athletes from 2000 to 2014, occurring most commonly in offensive linemen (28%). Surgically treated SLAP tears (42%) resulted in more days missed than did nonoperatively managed tears (140.2 vs 21.5 days; P < .001) and more games missed (8.4 vs 2.6 games; P = .003). SLAP repairs were also rare in NFL Combine athletes (n = 25 of 2965 athletes), with most having been performed in offensive linemen (32%). As compared with control NFL Combine athletes without SLAP tears, those drafted into the NFL with prior SLAP repair played significantly fewer games (33.7 vs 48.3; P = .049) and had fewer game starts (19.6 vs 35.4; P = .036). CONCLUSION: In this comprehensive analysis of SLAP tears in elite football players, it is clear that these injuries have the potential to cause significant detriment to an athlete's career.

Does the Level of Cervical Disc Herniation Surgery Affect Performance-based Outcomes in National Football League Athletes?

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The aim of this study was to determine whether the level of a cervical disc herniation (CDH) procedure will uniquely impact performance-based outcomes in elite athletes of the National Football League (NFL). SUMMARY OF BACKGROUND DATA: Comparative assessments of postsurgical outcomes in NFL athletes with CDH at different levels are unknown. Further, the surgical decision-making for these types of injuries in professional football athletes remains controversial. METHODS: NFL players with a CDH injury at a definitive cervical level were identified through a review of publicly available archives. Injuries were divided into upper- (C2-C4) and lower-level (C4-T1) CDH. The impact on player outcomes was determined by comparing return to play statistics and calculating a "Performance Score" for each player on the basis of pertinent statistical data, both before and after surgery. RESULTS: A total of 40 NFL athletes met inclusion criteria. In the upper-level group, 10 of 15 (66.6%) players successfully returned to play an average of 44.6 games over 2.6 years. The lower-level cohort had 18 of 25 (72%) players return to play with an average of 44.1 games over 3.1 years. There was no significant difference in the rate of return to play (P = 0.71). Postsurgical performance scores of the upper and lower-level groups were 1.47 vs. 0.69 respectively, with no significant difference between these groups (P = 0.06). Adjacent segment disease requiring reoperation occurred in 10% of anterior cervical discectomy and fusion patients. In 50% of foraminotomy patients, a subsequent fusion was required. CONCLUSION: A uniquely high percentage of upper-level disc herniations develop in NFL athletes, and although CDH injuries present career threatening implications, an upper-level CDH does not preclude a player from successfully returning to play at a competitive level. In fact, these athletes showed comparable postsurgical performance to those athletes who underwent CDH procedures at lower cervical levels. LEVEL OF EVIDENCE: 4.

The NFL Orthopaedic Surgery Outcomes Database (NO-SOD): The Effect of Common Orthopaedic Procedures on Football Careers.

BACKGROUND: Injuries are inherent to the sport of American football and often require operative management. Outcomes have been reported for certain surgical procedures in professional athletes in the National Football League (NFL), but there is little information comparing the career effect of these procedures. PURPOSE: To catalog the postoperative outcomes of orthopaedic procedures in NFL athletes and to compare respective prognoses and effects on careers. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Athletes in the NFL undergoing procedures for anterior cruciate ligament (ACL) tears, Achilles tendon tears, patellar tendon tears, cervical disc herniation, lumbar disc herniation, sports hernia, knee articular cartilage repair (microfracture technique), forearm fractures, tibial shaft fractures, and ankle fractures were identified through team injury reports or other public records. Game and performance statistics during the regular season were collected before and after surgery. Statistical analysis was performed with significance accepted as P < .05. RESULTS: A total of 559 NFL athletes were included. Overall, 79.4% of NFL athletes returned to play after an orthopaedic procedure. Forearm open reduction and internal fixation (ORIF), sports hernia repair, and tibia intramedullary nailing (IMN) led to significantly higher return-to-play (RTP) rates (90.2%-96.3%), while patellar tendon repair led to a significantly lower rate (50%) (P < .001). Athletes undergoing ACL reconstruction (ACLR), Achilles tendon repair, patellar tendon repair, and ankle fracture ORIF had significant declines in games played at 1 year and recovered to baseline at 2 to 3 years after surgery. Athletes undergoing ACLR, Achilles tendon repair, patellar tendon repair, and tibia IMN had decreased performance in postoperative season 1. Athletes in the Achilles tendon repair and tibia IMN cohorts recovered to baseline performance, while those in the ACLR and patellar tendon repair cohorts demonstrated sustained decreases in performance. CONCLUSION: ACLR, Achilles tendon repair, and patellar tendon repair have the greatest effect on NFL careers, with patellar tendon repair faring worst with respect to the RTP rate, career length after surgery, games played, and performance at 1 year and 2 to 3 years after surgery.

Preexisting Rotator Cuff Tears as a Predictor of Outcomes in National Football League Athletes.

BACKGROUND: A preexisting rotator cuff tear may affect the draft status and career performance of National Football League (NFL) players. HYPOTHESIS: Preexisting rotator cuff tears decrease a player's draft status, performance, and longevity in the NFL. STUDY DESIGN: Retrospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Medical reports of prospective NFL players during the NFL Scouting Combine from 2003 to 2011 were evaluated to identify players with a previous rotator cuff tear. Athletes were matched to control draftees without documented shoulder pathology by age, position, year drafted, and round drafted. Career statistics and performance scores were calculated. RESULTS: Between 2003 and 2011, 2965 consecutive athletes were evaluated. Forty-nine athletes had preexisting rotator cuff tears: 22 athletes underwent surgical intervention for their tear and 27 were treated nonoperatively. Those with a rotator cuff tear were significantly less likely to be drafted than those without a previous injury (55.1% vs 77.5%, P = 0.002). The 27 drafted athletes with preexisting rotator cuff tears started significantly fewer games (23.7 vs 43.0, P = 0.02) and played significantly fewer years (4.3 vs 5.7, P = 0.04) and significantly fewer games (47.1 vs 68.4, P = 0.04) than matched control athletes without rotator cuff tears. CONCLUSION: Athletes with a preexisting rotator cuff tear were less likely to be drafted and had decreased career longevity.

Different roles of the medial and lateral hamstrings in unloading the anterior cruciate ligament.

INTRODUCTION: Anterior cruciate ligament injuries are closely associated with excessive loading and motion about the off axes of the knee, i.e. tibial rotation and knee varus/valgus. However, it is not clear about the 3-D mechanical actions of the lateral and medial hamstring muscles and their differences in loading the ACL. The purpose of this study was to investigate the change in anterior cruciate ligament strain induced by loading the lateral and medial hamstrings individually. METHODS: Seven cadaveric knees were investigated using a custom testing apparatus allowing for six degree-of-freedom tibiofemoral motion induced by individual muscle loading. With major muscles crossing the knee loaded moderately, the medial and lateral hamstrings were loaded independently to 200N along their lines of actions at 0°, 30°, 60° and 90° of knee flexion. The induced strain of the anterior cruciate ligament was measured using a differential variable reluctance transducer. Tibiofemoral kinematics was monitored using a six degrees-of-freedom knee goniometer. RESULTS: Loading the lateral hamstrings induced significantly more anterior cruciate ligament strain reduction (mean 0.764 [SD 0.63] %) than loading the medial hamstrings (mean 0.007 [0.2] %), (P=0.001 and effect size=0.837) across the knee flexion angles. CONCLUSION: The lateral and medial hamstrings have significantly different effects on anterior cruciate ligament loadings. More effective rehabilitation and training strategies may be developed to strengthen the lateral and medial hamstrings selectively and differentially to reduce anterior cruciate ligament injury and improve post-injury rehabilitation. CLINICAL RELEVANCE: The lateral and medial hamstrings can potentially be strengthened selectively and differentially as a more focused rehabilitation approach to reduce ACL injury and improve post-injury rehabilitation. Different ACL reconstruction procedures with some of them involving the medial hamstrings can be compared to each other for their effect on ACL loading.

Common Shoulder Injuries in American Football Athletes.

American football is a collision sport played by athletes at high speeds. Despite the padding and conditioning in these athletes, the shoulder is a vulnerable joint, and injuries to the shoulder girdle are common at all levels of competitive football. Some of the most common injuries in these athletes include anterior and posterior glenohumeral instability, acromioclavicular pathology (including separation, osteolysis, and osteoarthritis), rotator cuff pathology (including contusions, partial thickness, and full thickness tears), and pectoralis major and minor tears. In this article, we will review the epidemiology and clinical and radiographic workup of these injuries. We also will evaluate the effectiveness of surgical and nonsurgical management specifically related to high school, collegiate, and professional football athletes.

Pre-existing lumbar spine diagnosis as a predictor of outcomes in National Football League athletes.

BACKGROUND: It is currently unknown how pre-existing lumbar spine conditions may affect the medical evaluation, draft status, and subsequent career performance of National Football League (NFL) players. PURPOSE: To determine if a pre-existing lumbar diagnosis affects a player's draft status or his performance and longevity in the NFL. STUDY DESIGN: Cohort study; Level 3. METHODS: The investigators evaluated the written medical evaluations and imaging reports of prospective NFL players from a single franchise during the NFL Scouting Combine from 2003 to 2011. Players with a reported lumbar spine diagnosis and with appropriate imaging were included in this study. Athletes were then matched to control draftees without a lumbar spine diagnosis by age, position, year, and round drafted. Career statistics and performance scores were calculated. RESULTS: Of a total of 2965 athletes evaluated, 414 were identified as having a pre-existing lumbar spine diagnosis. Players without a lumbar spine diagnosis were more likely to be drafted than were those with a diagnosis (80.2% vs. 61.1%, respectively, P < .001). Drafted athletes with pre-existing lumbar spine injuries had a decrease in the number of years played compared with the matched control group (4.0 vs. 4.3 years, respectively, P = .001), games played (46.5 vs. 50.8, respectively, P = .0001), and games started (28.1 vs. 30.6, respectively, P = .02) but not performance score (1.4 vs. 1.8, respectively, P = .13). Compared with controls, players were less likely to be drafted if they had been diagnosed with spondylosis (62.37% vs. 78.55%), a lumbar herniated disc (60.27% vs. 78.43%), or spondylolysis with or without spondylolisthesis (64.44% vs. 78.15%) (P < .001 for all), but there was no appreciable effect on career performance; however, the diagnosis of spondylolysis was associated with a decrease in career longevity (P < .05). Notably, 2 athletes who had undergone posterior lateral lumbar fusion were drafted. One played in 125 games, and the other is still active and has played in 108 games. CONCLUSION: The data in this study suggest that athletes with pre-existing lumbar spine conditions were less likely to be drafted and that the diagnosis is associated with a decrease in career longevity but not performance. Players with lumbar fusion have achieved successful careers in the NFL.

The impact of a cervical spine diagnosis on the careers of National Football League athletes.

STUDY DESIGN: Cohort study. OBJECTIVE: To determine the effect of cervical spine pathology on athletes entering the National Football League. SUMMARY OF BACKGROUND DATA: The association of symptomatic cervical spine pathology with American football athletes has been described; however, it is unknown how preexisting cervical spine pathology affects career performance of a National Football League player. METHODS: The medical evaluations and imaging reports of American football athletes from 2003 to 2011 during the combine were evaluated. Athletes with a cervical spine diagnosis were matched to controls and career statistics were compiled. RESULTS: Of a total of 2965 evaluated athletes, 143 players met the inclusion criteria. Athletes who attended the National Football League combine without a cervical spine diagnosis were more likely to be drafted than those with a diagnosis (P = 0.001). Players with a cervical spine diagnosis had a decreased total games played (P = 0.01). There was no difference in the number of games started (P = 0.08) or performance score (P = 0.38). In 10 athletes with a sagittal canal diameter of less than 10 mm, there was no difference in years, games played, games started, or performance score (P > 0.24). No neurological injury occurred during their careers. In 7 players who were drafted with a history of cervical spine surgery (4 anterior cervical discectomy and fusion, 2 foraminotomy, and 1 suboccipital craniectomy with a C1 laminectomy), there was no difference in career longevity or performance when compared with matched controls. CONCLUSION: This study suggests that athletes with preexisting cervical spine pathology were less likely to be drafted than controls. Players with preexisting cervical spine pathology demonstrated a shorter career than those without; however, statistically based performance and numbers of games started were not different. Players with cervical spinal stenosis and those with a history of previous surgery demonstrated no difference in performance-based outcomes and no reports of neurological injury during their careers.

Acromioclavicular joint injuries in the National Football League: epidemiology and management.

BACKGROUND: Previous studies investigating acromioclavicular (AC) joint injuries in professional American football players have only been reported on quarterbacks during the 1980s and 1990s. These injuries have not been evaluated across all position players in the National Football League (NFL). PURPOSE: The purpose of this study was 4-fold: (1) to determine the incidence of AC joint injuries among all NFL position players; (2) to investigate whether player position, competition setting, type of play, and playing surface put an athlete at an increased risk for this type of injury; (3) to determine the incidence of operative and nonoperative management of these injuries; and (4) to compare the time missed for injuries treated nonoperatively to the time missed for injuries requiring surgical intervention. STUDY DESIGN: Descriptive epidemiological study. METHODS: All documented injuries of the AC joint were retrospectively analyzed using the NFL Injury Surveillance System (NFLISS) over a 12-season period from 2000 through 2011. The data were analyzed by the anatomic location, player position, field conditions, type of play, requirement of surgical management, days missed per injury, and injury incidence. RESULTS: Over 12 NFL seasons, there were a total of 2486 shoulder injuries, with 727 (29.2%) of these injuries involving the AC joint. The overall rate of AC joint injuries in these athletes was 26.1 injuries per 10,000 athlete exposures, with the majority of these injuries occurring during game activity on natural grass surfaces (incidence density ratio, 0.79) and most often during passing plays. These injuries occurred most frequently in defensive backs, wide receivers, and special teams players; however, the incidence of these injuries was greatest in quarterbacks (20.9 injuries per 100 players), followed by special teams players (20.7/100) and wide receivers (16.5/100). Overall, these athletes lost a mean of 9.8 days per injury, with quarterbacks losing the most time to injury (mean, 17.3 days). The majority of these injuries were low-grade AC joint sprains that were treated with nonoperative measures; only 13 (1.7%) required surgical management. Players who underwent surgical management lost a mean of 56.2 days. CONCLUSION: Shoulder injuries, particularly those of the AC joint, occur frequently in the NFL. These injuries can result in time lost but rarely require operative management. Quarterbacks had the highest incidence of injury; however, this incidence is lower than in previous investigations that evaluated these injuries during the 1980s and 1990s.

Nerve block of the infrapatellar branch of the saphenous nerve in knee arthroscopy: a prospective, double-blinded, randomized, placebo-controlled trial.

BACKGROUND: With the rising use of outpatient knee arthroscopy over the past decade, interest in peripheral nerve blocks during arthroscopy has increased. Femoral nerve blocks are effective but are associated with an inherent risk of the patient falling postoperatively because of quadriceps weakness. We studied blocks of the infrapatellar branch of the saphenous nerve, which produce analgesia in the knee that is similar to that resulting from a femoral nerve block but without associated quadriceps weakness. METHODS: Thirty-four patients were enrolled into each arm of this prospective, randomized, double-blinded trial comparing 10 mL of 0.25% bupivacaine used as a block of the infrapatellar branch of the saphenous nerve with a placebo during simple knee arthroscopy. Immediate outcome measures included Numeric Rating Scale (NRS) pain scores (0 to 10 points), mobility and discharge times, opioid usage, subjective adverse side effects, and forty-eight-hour anesthesia recovery surveys. Short-term measures included one-week and twelve-week Lysholm knee scores. RESULTS: No adverse effects or increased quadriceps weakness were observed following use of the nerve block. Improvement in early NRS scores and subjective nausea (p = 0.03) were detected. Patients for whom the block was successful also had improved twelve-week Lysholm knee scores (p = 0.04). No differences in opioid usage, mobility time, forty-eight-hour anesthesia recovery scores, or one-week Lysholm knee scores were found. CONCLUSIONS: No significant adverse effect or disadvantage was identified for blocks of the infrapatellar branch of the saphenous nerve used in simple knee arthroscopy. In addition to decreased early NRS scores and nausea, blocks of the infrapatellar branch of the saphenous nerve demonstrated potential benefit at twelve weeks after simple knee arthroscopy.

Biomechanical comparison of 3 methods to repair pectoralis major ruptures.

BACKGROUND: Pectoralis major ruptures are closely associated with weight lifting and participation in sports. The anatomy of the pectoralis major tendon is unique with an elongated thin footprint requiring multiple points of fixation to restore the native anatomy. Multiple options exist for tendon repairs, but the strongest construct has yet to be identified. PURPOSE: The intent of this study was to compare the load to failure of bone trough, cortical button, and suture anchor repairs of the pectoralis major tendon in the extended and abducted position. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty fresh-frozen cadaveric shoulders were divided equally into 3 groups based on the repair technique to be performed. Bone mineral density of the surgical neck of the proximal humerus was assessed before each repair. Bone trough, suture anchor, and cortical button repairs were performed as dictated by computerized randomization. Each specimen was loaded to failure and mode of failure was noted. RESULTS: The majority of failures occurred through the suture used for tendon repair. One specimen in the bone trough group failed via fracture of the proximal humerus. The suture anchor group failed at the implant in 5 of 9 specimens and through the suture in 4 of 9 specimens. Load to failure was greatest in bone trough repairs at 596 N, followed by cortical button at 494 N, and finally suture anchor repairs with 383 N. Load to failure was significantly greater in the bone trough group when compared with suture anchor repairs (P = .007). No correlation was found between bone mineral density and load to failure. CONCLUSION: Bone trough repair of the pectoralis major tendon was stronger than suture anchor repair. CLINICAL RELEVANCE: Identification of the strongest repair may help guide surgical repair.

Biologic and pharmacologic augmentation of rotator cuff repairs.

As rotator cuff repair techniques have improved, failure of the tendon to heal to the proximal humerus is less likely to occur from weak tendon-to-bone fixation. More likely causes of failure include biologic factors such as intrinsic tendon degeneration, fatty atrophy, fatty infiltration of muscle, and lack of vascularity of the tendons. High failure rates have led to the investigation of biologic augmentation to potentially enhance the healing response. Histologic studies have shown that restoration of the rotator cuff footprint during repair can help reestablish the enthesis. In animal models, growth factors and their delivery scaffolds as well as tissue engineering have shown promise in decreasing scar tissue while maintaining biomechanical strength. Platelet-rich plasma may be a safe adjuvant to rotator cuff repair, but it has not been shown to improve healing or function. Many of these strategies need to be further defined to permit understanding of, and to optimize, the biologic environment; in addition, techniques need to be refined for clinical use.

Efficacy of preoperative home use of 2% chlorhexidine gluconate cloth before shoulder surgery.

HYPOTHESIS: Deep infection after shoulder surgery is a rare but devastating problem. This study tested the hypothesis that the home application of a 2% chlorhexidine gluconate cloth before shoulder surgery would be more efficacious than a standard shower of soap and water at decreasing the preoperative cutaneous levels of pathogenic bacteria on the shoulder. MATERIALS AND METHODS: This randomized, prospective study evaluated 100 consecutive patients undergoing shoulder surgery. Patients were randomly assigned to use 2% chlorhexidine gluconate-impregnated cloths (treatment group) or to shower with soap and water before surgery (control group). Cutaneous cultures were taken from the patients'shoulders in the preoperative holding area. Patients were monitored for 2 months postoperatively for clinical signs of infection. RESULTS: In the treatment group vs the control group, the overall positive culture rate was 66% vs 94% (P = .0008), and the positive culture rate for coagulase-negative Staphylococcus was 30% vs 70% (P = .0001). The positive culture rate for Propionibacterium acnes was 46% in the treatment group vs 58% in the control group (P = .32). No infections occurred in any patients at a minimum of 2-months after surgery. DISCUSSION: The use of the 2% chlorhexidine cloth was effective at decreasing overall bacterial culture rates before shoulder surgery and was particularly effective at decreasing the quantity of coagulase-negative Staphylococcus, a known causative agent of postoperative shoulder infections. CONCLUSION: Use of chlorhexidine impregnated cloths prior to shoulder surgery may be a useful adjunct to presently used infection prevention strategies.

Developing a 6-DOF robot to investigate multi-axis ACL injuries under valgus loading coupled with tibia internal rotation.

Anterior cruciate ligament (ACL) injuries have become more common in recent years as more young people participate in risky sporting activities [1]. Most ACL injuries occur as a result of noncontact mechanisms. Previous in vitro studies of ACL strain have found significant increases in ACL strain primarily with anterior directed force on the tibia relative to the femur and with internal rotation and often with valgus torque [2,3]. However, there remains significant controversy over the mechanisms of ACL failure and the forces on the knee that lead to injury. Some studies have also shown that isolated valgus loading may not load the ACL strongly. The goal of this study was to investigate the mechanism underlying valgus-related ACL injuries. An improved understanding of ACL failure may lead to improved ACL injury prevention programs. A novel 6 degrees of freedom (DOF) knee driving robot was developed in this study with a unique multi-axis simultaneous torque/position control. It was found that pure valgus torque caused a torque that internally rotated the tibia and thus increased ACL strain markedly, which may be an important mechanism underlying the rather common seemingly valgus-related ACL injuries.

In vivo patellar tracking induced by individual quadriceps components in individuals with patellofemoral pain.

Patellofemoral pain is a common knee disorder with a multi-factorial etiology related to abnormal patellar tracking. Our hypothesis was that the pattern of three-dimensional rotation and translation of the patella induced by selective activation of individual quadriceps components would differ between subjects with patellofemoral pain and healthy subjects. Nine female subjects with patellofemoral pain and seven healthy female subjects underwent electrical stimulation to selectively activate individual quadriceps components (vastus medialis obliquus, VMO; vastus medialis lateralis, VML; vastus lateralis, VL) with the knee at 0 degrees and 20 degrees flexion, while three-dimensional patellar tracking was recorded. Normalized direction of rotation and direction of translation characterized the relative amplitudes of each component of patellar movement. VMO activation in patellofemoral pain caused greater medial patellar rotation (distal patellar pole rotates medially in frontal plane) at both knee positions (p<0.01), and both VMO and VML activation caused increased anterior patellar translation (p<0.001) in patellofemoral pain compared to healthy subjects at 20 degrees knee flexion. VL activation caused more lateral patellar translation (p<0.001) in patellofemoral pain compared to healthy subjects. In healthy subjects the 3-D mechanical action of the VMO is actively modulated with knee flexion angle while such modulation was not observed in PFP subjects. This could be due to anatomical differences in the VMO insertion on the patella and medial quadriceps weakness. Quantitative evaluation of the influence of individual quadriceps components on patellar tracking will aid understanding of the knee extensor mechanism and provide insight into the etiology of patellofemoral pain.

Efficacy of surgical preparation solutions in shoulder surgery.

BACKGROUND: Deep infection following shoulder surgery is a rare but devastating problem. The use of an effective skin-preparation solution may be an important step in preventing infection. The purposes of the present study were to examine the native bacteria around the shoulder and to determine the efficacy of three different surgical skin-preparation solutions on the eradication of bacteria from the shoulder. METHODS: A prospective study was undertaken to evaluate 150 consecutive patients undergoing shoulder surgery at one institution. Each shoulder was prepared with one of three randomly selected solutions: ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol), DuraPrep (0.7% iodophor and 74% isopropyl alcohol), or povidone-iodine scrub and paint (0.75% iodine scrub and 1.0% iodine paint). Aerobic and anaerobic cultures were obtained prior to skin preparation for the first twenty patients, to determine the native bacteria around the shoulder, and following skin preparation for all patients. RESULTS: Coagulase-negative Staphylococcus and Propionibacterium acnes were the most commonly isolated organisms prior to skin preparation. The overall rate of positive cultures was 31% in the povidone-iodine group, 19% in the DuraPrep group, and 7% in the ChloraPrep group. The positive culture rate for the ChloraPrep group was lower than that for the povidone-iodine group (p < 0.0001) and the DuraPrep group (p = 0.01). ChloraPrep and DuraPrep were more effective than povidone-iodine in eliminating coagulase-negative Staphylococcus from the shoulder region (p < 0.001 for both). No significant difference was detected among the agents in their ability to eliminate Propionibacterium acnes from the shoulder region. No infections occurred in any of the patients treated in this study at a minimum of ten months of follow-up. CONCLUSIONS: ChloraPrep is more effective than DuraPrep and povidone-iodine at eliminating overall bacteria from the shoulder region. Both ChloraPrep and DuraPrep are more effective than povidone-iodine at eliminating coagulase-negative Staphylococcus from the shoulder.

In vivo three-dimensional mechanical actions of individual.

The flexor-pronator mass is thought to be the primary dynamic valgus stabilizer of the elbow and protects the ulnar collateral ligament. However, in vivo multiaxis actions of individual muscles of the flexor-pronator group and their roles in valgus stability have not been investigated quantitatively. This study tested the hypothesis that individual muscles of the flexor-pronator muscle group produce a significant varus moment that provides elbow valgus stability. The flexor carpi ulnaris, flexor carpi radialis, and pronator teres were selectively activated, and the resulting multiaxis moments at the elbow measured at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of elbow flexion using a six-axis force sensor were analyzed for their role in generating varus moment and protecting the ulnar collateral ligament. Considerable offaxis moments were generated by each muscle tested. Through the range of elbow flexion, the varus moment was the major component of the multiaxis action of the flexor carpi ulnaris (p < .001). The flexor carpi radialis and pronator teres had significant actions as elbow flexors and pronators (p < or = .032); these muscles also had a significant varus contribution at 90 degrees elbow flexion (p < or = .019). The results suggest that the flexor-pronator muscle group plays an important role in valgus stability of the elbow. In particular, the flexor carpi ulnaris creates a significant varus moment, which is important in unloading and protecting the ulnar collateral ligament. Rehabilitation and strengthening of the flexor-pronator muscle group may help prevent failure of the ulnar collateral ligament and may also help compensate for a medially insufficient elbow.