The efficacy of continuous cryotherapy on the postoperative shoulder: a prospective, randomized investigation.

This prospective, randomized investigation evaluated the efficacy of cryotherapy on subjective responses after both open and arthroscopic procedures on the shoulder. Seventy patients were randomly assigned to one of two study groups: (1) continuous cryotherapy group and (2) age-matched control group. Visual analog scales were used to assess subjective responses on postoperative days 1, 7, 14, and 21. On day 1, patients receiving cryotherapy reported significantly less pain during sleep and significantly more comfort in bed and rated their sleep as more restful than the control subjects. During days 7 through 21, cryotherapy subjects reported a significant reduction in frequency and intensity of pain, as well as less pain during shoulder rehabilitation, than the control subjects. These results indicate that cryotherapy is an effective method for postoperative pain control because it decreases the severity and frequency of pain and allows a return to normal sleep patterns while increasing overall postoperative comfort and satisfaction.

Motor control performance in the lower extremity: normals vs. anterior cruciate ligament reconstructed knees 5-8 years from the index surgery.

We compared motor control function in 50 patients who had undergone anterior cruciate ligament reconstruction using a bone-tendon-bone graft to that in 50 normal controls. Surgical subjects patients had undergone reconstruction with a one- (n=37) or two-incision (n=13) technique with the same rehabilitation protocol; mean time from the index surgery was 6.1 years (range of 5-8 years). For inclusion patients required an excellent outcome, category A IKDC score, and a KT-1000 side-to-side difference of 3 mm or less. Motor control evaluations were conducted using the KAT 2000 with static and dynamic tests. Normal controls had substantially better scores than did the surgical patients. There was no statistical difference the single-limb static test between scores of operated and nonoperated limbs. However, the operated limb scores were slightly better overall than those for the nonoperated limb, and the right knee scores tended to be better than those for the left knee. This may be explained by limb dominance. The test method employed in this investigation shows that anterior cruciate ligament reconstructed patients had a clear motor control deficit compared to normal control subjects even after several years.

Effect of lower extremity muscular fatigue on motor control performance.

PURPOSE: The purpose of this study was to determine whether lower extremity fatigue affects the ability of an individual to balance on an unstable platform. METHODS: Twenty healthy subjects (average age, 29 yr, range, 20 to 39 yr) were tested on an instrumented balance assessment system. Static tests were done on the limbs unilaterally and then bilaterally, and finally a dynamic test was performed in which the subject moved the platform in a circular manner to chase a moving object on a computer screen. After testing, subjects were fatigued using an isokinetic dynamometer, which imposes closed kinetic chain antagonistic exercise on the ankle, knee, and hip, similar to a stair stepper. No rest was allowed, and subjects were fatigued to less than 50% of their initial tested force. Subjects were then immediately retested on the unstable platform using the same testing protocol. All subjects completed the testing. RESULTS: Analysis of pre- and post-fatigue balance results demonstrated significant decreases in motor control performance on the three static tests following exercise to fatigue in all subjects (P < 0.001). CONCLUSIONS: Our findings support anecdotal evidence that fatigued individuals are at increased risk of injury because of loss of balance. Avoidance of fatigue and preconditioning may prevent injury.

The anterior band of the inferior glenohumeral ligament: biomechanical properties from tensile testing in the position of apprehension.

The shoulder is the most commonly dislocated joint in the body. The primary restraint to anterior instability is the anterior band of the inferior glenohumeral ligament, where lesions are found after dislocation. The amount of surgical plication required to eliminate instability and maintain full range of shoulder motion remains unclear. We performed tensile testing with the shoulder in abduction and external rotation in 11 human, fresh-frozen, cadaveric glenohumeral joints to improve understanding of the glenoid origin of the anterior band of the inferior glenohumeral ligament and to quantify midsubstance irrecoverable elongation. After measuring the length, width, and thickness of the anterior bands with digital micrometry, biomechanical properties were obtained on bone-ligament-labrum-bone (b-l-l-b) complexes. The complexes were aligned for tensile testing with the humerus abducted 60 degrees and externally rotated. The b-l-l-b complexes were then loaded to failure at a strain rate of 100%/sec. Seven of the complexes failed at the glenoid insertion site (representing the Bankart lesion), 2 at the humeral insertion site, and 2 at the anterior band midsubstance. The ultimate load for the b-l-l-b complexes was 353+/-32 N (mean+/-SE), and tensile stress at failure of the glenoid insertion site averaged 9.6+/-2.1 MPa. When the complex failed at the glenoid insertion site, total elongation of the b-l-l-b complex was 9.1+/-0.5 mm, and the ligament midsubstance strain was 13.0%+/-1.8%. Irrecoverable elongation was only 0.8 mm when failure occurred at the glenoid insertion site. Our results indicate patients with initial anterior glenohumeral instability have small irrecoverable capsuloligamentous elongation so that meaningful plication in addition to repair of the Bankart lesion may be unnecessary.

Interference screw fixation of hamstring vs patellar tendon grafts for anterior cruciate ligament reconstruction.

The present study was designed to investigate the fixation strength of a quadruple semitendinosus-gracilis graft compared with a middle-third bone-patellar tendon-bone graft using a new interference screw developed to fix hamstrings grafts for ACL reconstructions (RCL Smith & Nephew Donjoy). Five pairs of human cadaveric knees from donors with a mean age of 43 (range 33-52) years were used. One knee of each pair was randomly allocated to be reconstructed on the femoral side with a semitendinosus-gracilis graft from the same donor using RCL screw fixation. As the control, the contralateral knee was correspondingly reconstructed with a bone-patellar tendon-bone graft using the same interference screw. The grafts were pulled out at a velocity of 30 mm/s by an axially applied load using a MTS machine. The mean (SD) failure load for the bone-patellar tendon-bone graft fixations was 505 (25) N, 110% stronger than the mean failure load for the semitendinosus-gracilis graft fixations, which was 240 (47) N (P = 0.003). The stiffness for the patellar tendon-bone graft fixations was 46 (11) N/mm, 120% stiffer than the semitendinosus-gracilis graft fixations, which was 22 (11) N/mm (P = 0.01). This study shows that the interference screw principle used for ACL reconstructions with hamstrings tendons is inferior to that for bone-patellar tendon-bone reconstructions although the screw was developed especially for soft-tissue fixation in bone tunnels.

Strain of the anterior band of the inferior glenohumeral ligament during capsule failure.

Efficacious surgical treatment of glenohumeral instability requires a combination of anterior band origin repair and capsuloligamentous plication. The purpose of this article was to determine anterior band of the inferior glenohumeral ligament stretching at the time of glenohumeral failure. Thirteen fresh-frozen cadaver glenohumeral joints were thawed and dissected of soft tissue except for the capsuloligamentous structures. Testing was performed with a material testing system device, simulating the anterior instability apprehension position of the shoulder with 90 degrees of shoulder abduction and the humerus externally rotated until the bicipital groove was aligned with the supraglenoid tubercle. The length of each anterior band of the inferior glenohumeral ligament was obtained, and a variable reluctance transducer was applied to the anterior band midsubstance. Tensile testing at a strain rate of 100%/sec ensued until complete capsular failure occurred. Mid-substance strain of the anterior band of the inferior glenohumeral ligament at the time of capsular failure averaged 7.23% +/- 2.25% (mean +/- SD) with a range of 3.68% to 10.68%. Load to failure was 712.9 +/- 238.2 N (range 363.6 to 1136.9 N). All of the glenohumeral capsules failed at the glenoid origin, simulating a Bankart lesion, except for one that failed at the humeral insertion. When the intact capsuloligamentous tissue of the glenohumeral joint is tensile-tested in the apprehension position, there is only slight anterior band strain and failure occurring, predominantly at the glenoid insertion site. This has implications for the success of surgical procedures designed for acute repair of Bankart lesions.

Quadriceps muscle contraction protects the anterior cruciate ligament during anterior tibial translation.

The proposed skiing injury mechanism that suggests a quadriceps muscle contraction can contribute to anterior cruciate ligament rupture was biomechanically investigated. The effect of quadriceps muscle force on a knee specimen loaded to anterior cruciate ligament failure during anterior tibial translation was studied in a human cadaveric model. In both knees from six donors, average age 41 years (range, 31 to 65), the joint capsule and ligaments, except the anterior cruciate ligament, were cut. The quadriceps tendon, patella, patellar tendon, and menisci were left intact. One knee from each pair was randomly selected to undergo destructive testing of the anterior cruciate ligament by anterior tibial translation at a displacement rate of 30 mm/sec with a simultaneously applied 889 N quadriceps muscle force. The knee flexion during testing was 30 degrees. As a control, the contralateral knee was loaded correspondingly, but only 5 N of quadriceps muscle force was applied. The ultimate load for the knee to anterior cruciate ligament failure when tested with 889 N quadriceps muscle force was 22% +/- 18% higher than that of knees tested with 5 N of force. The linear stiffness increased by 43% +/- 30%. These results did not support the speculation that a quadriceps muscle contraction contributes to anterior cruciate ligament failure. In this model, the quadriceps muscle force protected the anterior cruciate ligament from injury during anterior tibial translation.

A review of selected noncontact anterior cruciate ligament injuries in the National Football League.

During five football seasons, from 1989 through 1993, 61 surgically proven, noncontact, anterior cruciate ligament injuries, were identified from among 22 National Football League teams. The variables of surface, shoe type, playing conditions, and whether or not the shoe was spatted were identified for each reported injury. Forty noncontact injuries occurred in conventional cleated shoes on natural grass, and 21 occurred on an artificial surface. Almost half of all injuries (47.5%) occurred during game-day exposures despite the fact that the practice versus game-day exposure rate was 5:1. Of these injuries, 95.2% (N = 58) occurred on a dry field. The factors of cleat and shoe type, type of surface (natural versus artificial), surface conditions (wet/dry), and the effect of "spatting" a shoe are presented. The significance of these factors and their likelihood to be associated with injury is analyzed by use of a statistical tool, the incidence density ratio.

Differences in friction and torsional resistance in athletic shoe-turf surface interfaces.

This study evaluated the shoe-surface interaction of 15 football shoes made by 3 manufacturers in both anterior translation and rotation using a specially designed pneumatic testing system. The shoes included traditional cleated football shoes, "court" shoes (basketball-style shoes), molded-cleat shoes, and turf shoes. Under an 11.35-kg (25-pound) axial load, all shoes were tested on synthetic turf under wet and dry conditions and on natural stadium grass. Test-retest reliability, as calculated using the Pearson Product-Moment Correlation test, was 0.85 for force of translation and 0.55 for the moment of rotation. The wet versus dry surface values on translation were significantly different for rotation about the tibial axis. Spatting, which is protective taping of the ankle and heel applied on the outside of the shoe, resulted in a reduction of forces generated in both translation and rotation. No overall difference between shoes on grass versus AstroTurf was noted. However, there were significant differences for cleated and turf shoes. Shoes tested in conditions for which they were not designed exhibited reproducible excessive or extreme minimal friction characteristics that may have safety implications. On the basis of this study, we urge shoe manufacturers to display suggested indications and playing surface conditions for which their shoes are recommended.

Bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction: the effects of graft pretensioning.

Viscoelastic creep is a well-known phenomenon associated with collagenous soft tissues under sustained tensile load. Despite our understanding of this phenomenon and the potential for "loosening" of the graft over time, pretensioning of bone-patellar tendon-bon (B-PT-B) grafts for reconstruction of the anterior cruciate ligament (ACL) to eliminate this elastic deformation is not commonly practiced. This investigation quantified viscoelastic creep in B-PT-B grafts using both an in vivo and an in vitro model. In vivo, 10-mm B-PT-B grafts were procured and prepared in a standard manner for arthroscopically assisted ACL reconstruction. A total of 153 grafts were evaluated. During preparation, each graft was tensioned using a commercially available graft preparation board (Smith & Nephew DonJoy). An initial tensile load of 2.25 N (0.5 lb) was applied to the graft and a measurement was taken between bone-tendon junctions at either end. A sustained load of 89 N (20 lb) was then applied for a minimum of 4 minutes and the measurement repeated. In the in vitro model, grafts were harvested in a standard manner, then placed in a servohydraulic for tensile loading. A differential variable reluctance transducer was implanted in each graft to quantify net displacement during 15 minutes of sustained tensile loading at 89 N (20 lb). A total of 13 specimens were evaluated. In the in vivo model, mean pretension bone-tendon junction length was 43.6 mm (range, 29 to 64 mm; SD, +/- 6.7). Mean post-tension bone-tendon length was 49.6 mm (range, 33 to 71 mm; SD, +/- 7.1), representing a mean increase in length of 6.0 mm (range, 2 to 12; SD, +/- 2.1) or 14.0% (range, 3.8 to 28.6; SD, +/- 5.2). In the in vitro model, the mean pretension tendon length was 42.81 m (range, 35.20 to 51.48; SD, 4.54). The mean post-tension length was 47.11 mm (range, 38.05 to 56.23; SD, +/- 5.04) representing a mean increase of 4.30 mm or 10.12%. These data would seem to support the hypothesis that without pretensioning, significant postimplantation graft creep will occur.

Fixation strength of rotator cuff repairs with suture anchors and the transosseous suture technique.

The strength of classic transosseous suture repair of rotator cuff tendons was compared with similar repairs with four "third-generation" suture anchors. Results demonstrate the repair construct selected had a significant influence on failure at ultimate load (p = 0.005). Among the anchors tested the Statak design was significantly stronger than the other three. Furthermore Statak, Harpoon, and Superanchor designs were all significantly stronger than the Revo screw. No significant difference was seen between the strength of repairs performed with the Statak, the Harpoon, or the Superanchor compared with the transosseous suture technique. The transosseous suture technique was significantly stronger than repairs performed with the Revo. We conclude suture anchor design has evolved to a point where initial fixation of torn rotator cuff tendons is equivalent to more traditional techniques using only sutures.

Soft tissue reconstruction in the shoulder. Comparison of suture anchors, absorbable staples, and absorbable tacks.

We evaluated three mechanical soft tissue fixation devices (SuperAnchor, Suretac, and the Instrument Makar [IM] Bioabsorbable Staple) in a cadaveric model by examining ultimate tensile failure and modes of failure in simulated Bankart repairs. We attempted to realistically evaluate the strengths of soft tissue reattachment procedures at the anterior glenoid under worst-case conditions--load to failure. Twenty fresh-frozen cadaveric shoulders were used in this investigation. Each of the three techniques was performed in each anterior glenoid rim at one of three locations: superior, middle, or inferior. The subscapularis muscle-tendon was harvested, used in the repair, and loaded to failure. The mean load at failure for the SuperAnchor was 217.32 N; for the IM Staple, 132.32 N; and for the Suretac, 122.37 N. A two-sample t-test demonstrated that the load at failure for the SuperAnchor was statistically greater (P < 0.001) when compared with the IM Staple and Suretac. There was no statistical difference between load at failure for the Suretac and the IM Staple. The most common failure mode for the Mitek was suture breakage (71%). Anchor pullout from bone was the most common failure mode for the IM Staple (75%) and Suretac (94%).

Rehabilitation of anterior cruciate ligament injuries.

Rehabilitation of the anterior cruciate ligament absent or reconstructed knee is becoming a true artform. Accelerated, but controlled rehabilitation, is becoming more commonplace. Scientific-based data along with clinical experiences are the basis of the rehabilitation guidelines brought forth in this article. Anterior cruciate ligament strain and implications for exercise, continuous passive motion, proprioceptive exercise, and the role of knee bracing are all discussed in relation to the overall rehabilitation program.

Biomechanics of the lateral ligaments of the ankle: an evaluation of the effects of axial load and single plane motions on ligament strain patterns.

Strain behavior in the anterior talofibular and calcaneofibular ligaments of the ankle, with and without axial load, was evaluated using human cadaveric specimens, a specially designed instrumented test fixture, and Hall-Effect strain transducers. Ligament strain patterns were significantly altered with axial loading in some conditions. This data may have clinical relevance both in the diagnosis and rehabilitation of lateral ligament injuries.

Impact biomechanics of lateral knee bracing. The anterior cruciate ligament.

We evaluated the effects of six different prophylactic braces on ACL ligament strain under dynamic valgus loads using a mechanical surrogate limb validated against human cadaveric specimens. Medical collateral ligament and anterior cruciate ligament peak forces, medial collateral ligament and anterior cruciate ligament tension initiation times, and impact safety factors were calculated for both braced and unbraced conditions. These tests were conducted to determine whether or not application of a prophylactic brace might provide protection to the anterior cruciate ligament under valgus loading conditions. The results of this study indicate that those braces that increased impact duration appear to differentially protect the anterior cruciate ligament more than the medial collateral ligament, and that most of the braces tested appear to provide some degree of protection to the anterior cruciate ligament under direct lateral impacts. These findings should be confirmed clinically.

The current state of functional knee bracing research. A review of the literature.

This paper reviews recent research on functional knee bracing. Research is categorized by subject, approach, or technique. The authors conclude that, while there is a good deal of excellent research available, there is little data to assist the clinician in selecting an orthosis for a specific application. The authors recommend that future investigations address the physiologic aspects of functional knee bracing and that brace manufacturers assume more responsibility in the validation of both existing and future brace designs.

Choosing functional knee braces.

Choosing a functional brace for knee injury is a complex issue complicated by a lack of quantitative research on the subject and an increasing number of braces currently on the market. The correct brace decision will be facilitated by a better understanding of knee injury biomechanics and by a thorough understanding of the choices available. The ultimate selection of a brace should be based on sound mechanical criteria and individualized for each patient. The brace must be mechanically effectual and one the patient likes, has confidence in, and will tolerate. In combination with aggressive rehabilitation, the functional brace can make a significant contribution to returning individuals to functional activity.

Comparison of rehabilitative knee braces. A biomechanical investigation.

A biomechanical comparison of eight popular commercially available rehabilitative knee braces was undertaken using a specially designed mechanical surrogate and computerized data acquisition system. Tests conducted included passive extension, valgus rotation, and anterior-posterior tibial translation. Most of the braces tested significantly reduced both translations and rotations compared to the unbraced limb under static test conditions. Braced versus braced performance varied and was found to depend upon a number of mechanical and design factors.