The effects of modified posterior tibial slope on anterior cruciate ligament strain and knee kinematics: a human cadaveric study.

Increases to the posterior tibial slope can lead to an anterior shift in tibial resting position. However, the effect of this shift on anterior cruciate ligament (ACL) strain has not been investigated sufficiently. This study examined the relationship between increased tibial slope and ACL strain, as well as the subsequent kinematics of the tibiofemoral joint. We hypothesized increases in slope would shift the tibia anterior relative to the femur and increase ACL strain. Anterior cruciate ligament strain measurements and tibiofemoral kinematics were compared for 5 intact and experimental knees subject to anterior opening wedge osteotomy. Combinations of both compressive and AP loading were applied. As slope increased, the resting position of the tibia shifted anteriorly, external tibial rotation increased, and tibial translation remained unchanged. Contrary to our hypothesis, ACL strain decreased. The clinical implication of these findings is that alterations to the posterior tibial slope should not increase strain in the ACL.

Radiographic and histologic findings of vertebral augmentation using polymethylmethacrylate in the primate spine: percutaneous vertebroplasty versus kyphoplasty.

STUDY DESIGN: Animal study. OBJECTIVES: To investigate the gross behavior and the histologic effect(s) of polymethylmethacrylate (PMMA) in primate vertebral bodies after percutaneous vertebroplasty and kyphoplasty. SUMMARY OF BACKGROUND DATA: PMMA is known to induce thermal osteonecrosis in exposed bone during tumor surgery and total joint arthroplasty, and barium sulfate as well as PMMA are known to induce a foreign body reaction, but the effects of PMMA on vertebral cancellous bone have not been well documented. Furthermore, little is known about the mechanisms of cement extravasation that occasionally occur during these procedures. Lastly, it is not known if differences exist between vertebroplasty and kyphoplasty with regards to the above occurrences. METHODS: Six living, elderly, female baboons were used in this study. Seven vertebrae from T12 to L6 were investigated in each animal. Two levels underwent vertebroplasty, two underwent kyphoplasty, and one underwent cavity creation only without cement augmentation in each animal. Three animals were killed at 24 hours and three at 26 weeks after surgery. The specimens were examined macroscopically for cement migration, and histologically for evidence of thermal necrosis, foreign body reaction, cement migration, and intravascular extravasation. RESULTS: Small zones of osteonecrosis were observed histologically at the bone-cement interface in only two kyphoplasty (2 of 6) and two vertebroplasty specimens (2 of 5) at 26 weeks after surgery. All of these necrotic segments of bone were associated with new bone formation. Foreign body reactions were observed in all specimens at 26 weeks after surgery, yet none of them was associated with bone resorption. The incidence of cement leak into the spinal canal and adjacent soft tissues was 6 of 11 and 4 of 11 in vertebroplasty specimens and 5 of 12 and 3 of 12 in kyphoplasty specimens, respectively. There was no statistical difference in the incidence of cement leakage into the spinal canal (P = 0.54) and adjacent soft tissues (P = 0.55) between vertebroplasty and kyphoplasty specimens. The incidence of intravascular cement was significantly greater in vertebroplasty (11 of 12, 91%) than in kyphoplasty (5 of 12, 42%) (P = 0.013). CONCLUSIONS: PMMA caused relatively little necrotic exothermal effect. The presence of PMMA with barium sulfate induces a mild foreign body reaction. The use of a balloon tamp creates a void by displacing pieces of bone, which may result in a lower incidence of intravascular cement leak.

Return to play issues in upper extremity injuries.

OBJECTIVE: The purpose of this paper is to outline general treatment and return to play (RTP) strategies as they pertain to athletes with various upper extremity injuries. It is not intended to be a comprehensive review of these injuries. DATA SOURCES/SYNTHESIS: A review of the literature plus expert opinion served as the basis for recommendations made regarding management strategies for returning the athlete to play after upper extremity injury. A Medline search was performed using the following key words: upper extremity injury, return to play, glenohumeral dislocation, acromioclavicular joint sprains, elbow dislocation, scaphoid fracture, metacarpal fracture, finger dislocation, tendon injury, hand, mallet finger, and jersey finger. These and other related terms were crossed using the Medline database from 1966 to 2005. RESULTS: Review of book chapters, articles generated from the Medline search, and expert opinion led to the recommendations that are presented here. There is general agreement regarding the treatment of many of the injuries discussed, but controversies do exist. RTP guidelines are largely dependent on the severity of initial injury, rates of healing, and return of strength. CONCLUSIONS: Each athlete with a particular injury to the upper extremity needs to be approached as an individual as no single set of treatment or RTP guidelines applies to all injuries or all individuals. Factors such as age, injury severity, hand dominance, type of sport participation, method of treatment, and chronicity of injury are among the many issues that must be considered when developing a treatment and RTP strategy for a particular athlete.