Torsional Fracture of the Humerus after Subpectoral Biceps Tenodesis with an Interference Screw: A Biomechanical Cadaveric Study.

BACKGROUND: Humeral fracture following subpectoral biceps tenodesis has been previously reported; however, there are no published biomechanical studies reporting the resulting torsional strength of the humerus. Our purpose was to determine if there is an increased risk of humerus fracture after subpectoral biceps tenodesis with an interference screw and to determine if screw size is also a factor. We hypothesized that limbs receiving the procedure would have reduced failure torque and rotation under external rotation compared to untreated controls and that the larger screw size would result in inferior mechanical properties compared to the smaller. METHODS: Twenty matched pairs of embalmed cadaveric humeri were subjected to subpectoral biceps tenodesis using either a 6.25 or 8.0mm interference screw, with the untreated contralateral limb serving as a control. Each humerus was mechanically tested in torsional external rotation to failure. FINDINGS: Maximum torque and rotation to failure were reduced in the tenodesis group compared to controls; however, there was no difference between screw sizes. When both screw sizes were combined into a single group, paired t-tests also showed similar differences. INTERPRETATION: Based on our experiment, there is an increased risk for humerus spiral fracture when subjected to torsional external rotation after subpectoral biceps tenodesis with an interference screw compared to an intact humerus; however, there is not a significant difference between a 6.25mm and 8.0mm screw. Surgeons may elect to use alternative fixation methods in patients at high risk (e.g., overhead throwing athletes, etc.) for torsional loads and fracture.

Why spin contamination is a major problem in the calculation of spin-spin coupling in triplet biradicals.

In organic triplet biradicals, zero field splitting is dominated by the spin-dipolar interaction. While it has been observed before that spin-unrestricted density functional calculations give huge errors for systems with small D values, a consistent explanation was still missing. Using model systems, this work demonstrates how spin contamination creates unphysical one-center terms in the two-particle density matrix that spoil the calculated results.

The ulnar collateral ligament procedure revisited: the procedure we use.

CONTEXT: The ulnar collateral ligament of the elbow (UCL) is frequently injured in throwing athletes, most commonly baseball pitchers. The ligament is reconstructed through bone tunnels using palmaris longus or gracilis autograft. RESULTS: This study highlights the following technique for UCL reconstruction in over 2000 athletes.(2) CONCLUSION: When conservative management fails, ligament reconstruction can allow the athlete to return to their sport.(1).

Suture number determines strength of rotator cuff repair.

BACKGROUND: Failure of surgical repair of a rotator cuff tear continues to be a clinical problem. For other tendon repairs, increasing the number of sutures improves both biomechanical performance and clinical outcomes. Several investigators have shown biomechanical advantages of double-row techniques but have used many more sutures than were used with the single-row techniques with which the double-row techniques were compared. The purposes of our study were to establish whether using a greater number of sutures would improve the biomechanical properties of a rotator cuff repair model, and whether using equal numbers of sutures would lead to equivalent results between single and double-row configurations. METHODS: Fresh-frozen sheep infraspinatus tendons underwent single-row repair with two, four, or six mattress sutures and double-row repair with use of four mattress sutures. Specimens were pretensioned at 10 N for one minute, then cycled from 10 to 180 N for 200 cycles at 0.2 Hz; this was followed by load to failure. Cyclic gap formation, failure load, and failure type were recorded. RESULTS: The four-suture single-row and four-suture double-row repairs had similar gap formation during cyclic testing, with no significant differences between them. Cyclic gap formation in the two-suture single-row group was 6.7 and 7.1 mm (97% and 109%) greater than that in the four and six-suture single-row groups after 200 cycles (p < 0.001). The average loads to failure of the two, four, and six-suture single-row groups were 274, 362, and 572 N (p < 0.0001). The average load to failure of the four-suture double-row group was 386 N, which was similar to the value in the four-suture single-row group (p = 0.58). CONCLUSIONS: In an ovine rotator cuff tendon repair model, increasing the number of sutures decreased cyclic gap formation and increased load to failure. Single and double-row repairs are biomechanically equivalent when the number of sutures is kept constant. CLINICAL RELEVANCE: The results of this study support the use of greater numbers of sutures in rotator cuff repair and disagree with the assertion that double-row repairs are biomechanically superior to single-row repairs.

Incidence and variance of foot and ankle injuries in elite college football players.

We conducted a study on the risk for foot and ankle injuries in college football players on the basis of injury type and player position. In February 2006, we evaluated 320 intercollegiate football players at the National Football League Combine. All pathologic conditions and surgical procedures of the foot and ankle were recorded, and data were analyzed by player position to detect any trends. Seventy-two percent (n = 231) of the players had a history of foot and ankle injuries, with a total of 287 foot and ankle injuries (1.24 injuries/player injured). The most common injuries were lateral ankle sprain (n = 115), syndesmotic sprain (50), metatarsophalangeal dislocation/turf toe (36), and fibular fracture (25). Foot and ankle injuries were most common in kickers/punters (100% incidence), special teams (100%), running backs (83%), wide receivers (83%), and offensive linemen (80%). Lateral ankle sprains, the most common injuries, were treated surgically only 2.6% of the time. Offensive linemen were most likely to have had syndesmotic sprains (32%), and quarterbacks had the highest incidence of fibular fractures (16%). Foot and ankle injuries are common in collegiate football players, affecting 72% of players. Thirteen percent underwent surgical treatment. Trends are seen in the types of injuries for the different player positions.

Zero-field splittings from density functional calculations: analysis and improvement of known methods.

Several different approaches have been proposed to calculate the zero-field splitting tensor with density functional methods. In this work, our own derivation is presented in some detail, to allow a theoretical analysis and a comparison with other methods [M. R. Pederson and S. N. Khanna, Phys. Rev. B 60, 9566 (1999); F. Neese, J. Am. Chem. Soc. 128, 10213 (2006); J. Chem. Phys. 127, 164112 (2007)]. Pederson's method can be improved by properly taking into account the quantum nature of spin when extracting the zero field splitting tensor from the magnetic anisotropy. A closed-shell molecule at large distance from an open shell complex will have a spurious contribution to the zero-field splitting tensor calculated with Neese's methods. We thus have analyzed his approach in some detail and found that it can be corrected if one properly transforms the equations used in wave function based theory to a sum-over-states type expression before one interprets it as an energy derivative. If improved along these lines, Neese's and Pederson's methods become identical down to the working equations. The theoretical analysis is illustrated by sample calculations on the well-studied Mn(III)-tris-acetylacetonato complex Mn(acac)(3), both as an isolated molecule and with a Pd(II) dichloro diammine complex at large distance as an innocent spectator.

Total shoulder arthroplasty utilizing mini-stem humeral components: technique and short-term results.

INTRODUCTION: Throughout the field of orthopedic surgery, there has been a trend toward using smaller incisions and implants that preserve as much normal anatomy as possible. The use of bone sparing technology, such as partial and full surface replacements of the humeral head, while attractive in younger patients, does not allow the best exposure for proper glenoid replacement. Additionally, there are other situations when the use of surface replacements is contraindicated. There are also patients with an existing total elbow replacement or a humeral malunion or deformity in which a traditional long-stem component would not fit. For these reasons, a mini-stem humeral component for total shoulder arthroplasty was developed. In this study, we hypothesized that total shoulder replacement using the mini-stem humeral component could provide low complication rates and good to excellent results, as measured by postoperative Constant-Murley and UCLA shoulder scores at minimum 2 years postoperatively. MATERIALS AND METHODS: This was a retrospective review of the first 49 mini-stem shoulder replacements (47 patients) for primary osteoarthritis. There were 26 male and 23 female patients. UCLA Shoulder Score and Constant Murley Scores were obtained on all patients at a minimum of 2 years postoperatively (average 29 months; range 24-43 months). Radiographs were interpreted by a musculoskeletal radiologist. Intraoperative blood loss was documented as was postoperative pain using a visual analog pain scale. RESULTS: Patients experienced over 90% good to excellent results at minimum 2 year follow up. ROM improved significantly in all parameters. Postoperative UCLA scores at final follow up averaged 27.5 while Constant-Murley scores averaged 91. Small lucent lines (<1 mm) were noted in 11 patients. Five of 49 stems were placed in varus but the postoperative result was not affected in any of these patients. One patient suffered an acute subscapularis rupture that required repair. CONCLUSIONS: This is the first report to document the efficacy of mini-stemmed humeral components used during total shoulder arthroplasty. Our study group showed good to excellent results as well as improvement in range of motion at minimum 2-year follow-up. The results presented in this study are comparable to previous outcomes achieved with conventional length humeral components, and suggest that mini-stem humeral components are an effective option for total shoulder arthroplasty.

Allograft use in anterior cruciate ligament reconstruction.

Anterior cruciate ligament (ACL) reconstruction is one of the most common procedures performed by orthopedic surgeons. While autograft reconstruction remains the gold standard, allograft tissues have become a controversial option for ACL reconstruction. No data currently exist regarding recent trends in graft choices, and no consensus exists over which graft type is most appropriate for which patient. In this article, we examine trends in ACL graft choice at our institution, and review the pertinent information a surgeon must consider when making this decision. We reviewed operating room records from 2002 to 2008 to determine trends in graft choice for primary single bundle ACL reconstruction. Total number of procedures performed, graft choices, and patient ages were recorded. Patients were divided into the following age groups: less than 16, 16 to 20, 21 to 30, 31 to 40, 41 to 50, and over 50. Percent of ACL reconstructions using allograft was calculated for each year, as well as for each age group. Data were analyzed for trends in ACL graft choice over this time period as well as for trends in graft choice by age. We hypothesized that the rate of allograft use in primary ACL reconstruction had increased over time and that allograft use was associated with higher patient age. We also review the risks, safety, and standards for tissue procurement. Allograft use increased significantly (p < 0.001) from 2002 (17%) to 2008 (46%). There was also a significant difference (p < 0.001) in average age of patients receiving allografts (40.4 years) and autografts (26.4 years). Allograft use was significantly associated with higher patient age (p < 0.05) and increased with each successive age group from a rate of 9.9% in patients under 16 to 79.9% in patients over 50. Our study found that allograft use in primary ACL reconstruction has significantly increased from 2002 to 2008 and is significantly more common in older patients.

Paraspinal muscle impingement causing acute Brown-Sequard syndrome after posterior cervical decompression.

STUDY DESIGN: A case report. OBJECTIVE: To present a previously unreported cause of neurologic compromise after cervical spine surgery. SUMMARY OF BACKGROUND DATA: Several different causes of postoperative neurologic deficit have been reported in the literature. The authors present a case of acute postoperative paralysis after posterior cervical decompression by a mechanism that has not yet been reported in the literature. METHODS: A 54-year-old muscular, short-statured man underwent posterior cervical laminectomy from C3-C5 without instrumentation and left C5 foraminotomy. Within hours of leaving the operating room, he began to develop postoperative neurologic deficits in his extremities, which progressed to a classic Brown-Sequard syndrome. Magnetic resonance imaging revealed regional kyphosis and large swollen paraspinal muscles impinging on the spinal cord without epidural hematoma. Emergent operative re-exploration confirmed these findings; large, swollen paraspinal muscles, a functioning drain, and no hematoma were found. RESULTS: The patient was treated with immediate corticosteroids at the time of initial diagnosis, and emergent re-exploration and debulking of the paraspinal muscles. The patient had complete recovery of neurologic function to his preoperative baseline after the second procedure but required a third procedure in which anterior discectomy and fusion at C4-C5 was performed, which led to improvement of his preoperative symptoms. CONCLUSION: When performing posterior cervical decompression, surgeons must be aware of the potential for loss of normal lordosis and anterior displacement of paraspinal muscles against the spinal cord, especially in muscular patients.

Incidence and variance of knee injuries in elite college football players.

Knee injuries are among the most common musculoskeletal injuries in US football players. The literature includes little information about the role of player position and risk for knee injury. We hypothesized that the incidence of knee injury in elite collegiate US football players is high and that type of injury varies by player position. We evaluated 332 elite collegiate US football players at the 2005 National Football League Combine. All players underwent radiographic examinations, including plain x-rays and/or magnetic resonance imaging when necessary. All knee pathologic conditions and surgical procedures were recorded. Data were analyzed by player position to detect any trends. Fifty-four percent (179) of the 332 players had a history of knee injury; knee injuries totaled 233 (1.3/player injured). Eighty-six players (25.9%) had a total of 114 surgeries. The most common injuries were medial collateral ligament injury (n = 79), meniscal injury (n = 51), and anterior cruciate ligament (ACL) injury (n = 40). The most common surgeries were arthroscopic meniscectomy (n = 39), ACL reconstruction (n = 35), and arthroscopic meniscal repair (n = 13). A history of knee injury was most common in defensive linemen (68% of players), tight ends (57%), and offensive linemen (57%). Knee surgery was more commonly performed on running backs (36%) and linebackers (34%). There were no significant associations between type or frequency of specific injuries with regard to player position. Knee injuries are common injuries in elite collegiate football players, and one fourth of these players undergo surgical procedures. However, there were no statistically significant differences in type or frequency of injuries by player position.

Prevalence and variance of shoulder injuries in elite collegiate football players.

BACKGROUND: Shoulder injuries are the fourth most common musculoskeletal injury encountered in American football players. There is little information in the literature on the role of playing position in the type of shoulder injuries seen. HYPOTHESIS: There is a high prevalence of shoulder injuries in elite collegiate American football players, with type of injury varying by playing position. STUDY DESIGN: Cohort study (prevalence); Level of evidence, 3. METHODS: A total of 336 elite collegiate American football players were invited to the National Football League Combine for physical testing and medical evaluation. Current and historical data were evaluated for the purpose of this study, and all players underwent radiographic examinations, including plain radiographs and/or magnetic resonance imaging when necessary. All shoulder pathological conditions and shoulder surgical procedures were recorded. Players were categorized by position for the analysis of position-specific trends. RESULTS: Of the players, 50% had a history of shoulder injuries, with a total of 226 shoulder injuries (1.3 injuries per player injured); 56 players (34%) had a total of 73 surgeries. The most common injuries were acromioclavicular separation (41%), anterior instability (20%), rotator cuff injury (12%), clavicle fracture (4%), and posterior instability (4%). The most common surgeries performed were anterior instability reconstruction (48%), Mumford/Weaver-Dunn surgery (15%), posterior instability surgery (10%), and rotator cuff surgery (10%). Shoulder injuries were more common in quarterbacks and defensive backs. Surgery was more common in linebackers or linemen. A history of anterior instability was more common in defensive players, with surgery required 76% of the time. Linemen had more rotator cuff injuries and posterior instability than players in other positions. CONCLUSION: Shoulder injuries are common injuries in elite collegiate football players, with one-third undergoing surgical procedures. There are definitive trends in the types of injuries per player position.