In vitro characterization of the relationship between the Q-angle and the lateral component of the quadriceps force

Although the Q-angle is routinely measured, the relationship between the Q-angle and the lateral component of the quadriceps force acting on the patella is unknown. Five cadaver knees were flexed on a knee simulator with a normal Q-angle, and flexed after increasing and decreasing the Q-angle by shifting the quadriceps origin laterally and medially, respectively. The motion of the femur, tibia and patella was tracked from 20 to 90° of flexion using electromagnetic sensors. The motion of landmarks used to quantify the Q-angle was tracked to determine the ‘dynamic Q-angle’ during flexion. The lateral component of the force applied by the actuator secured to the quadriceps tendon was also quantified throughout flexion. Increasing the initial Q-angle significantly (p < 0.05) increased the dynamic Q-angle and the lateral force exerted through the quadriceps tendon throughout flexion. Decreasing the initial Q-angle significantly decreased the dynamic Q-angle at 90° of flexion and significantly decreased the lateral force exerted through the quadriceps tendon from 20 to 40° of flexion. Even though the dynamic Q-angle changes during flexion, an abnormally large initial Q-angle can be an indicator of an abnormally large lateral force acting on the patella during flexion.

Q-angle influences tibiofemoral and patellofemoral kinematics

Numerous surgical procedures have been developed to correct patellar tracking and improve patellofemoral symptoms by altering the Q-angle (the angle between the quadriceps load vector and the patellar tendon load vector). The influence of the Q-angle on knee kinematics has yet to be specifically quantified, however. In vitro knee simulation was performed to relate the Q-angle to tibiofemoral and patellofemoral kinematics. Six cadaver knees were tested by applying simulated hamstrings, quadriceps and hip loads to induce knee flexion. The knees were tested with a normal alignment, after increasing the Q-angle and after decreasing the Q-angle. Increasing the Q-angle significantly shifted the patella laterally from 20 degrees to 60 degrees of knee flexion, tilted the patella medially from 20 degrees to 80 degrees of flexion, and rotated the patella medially from 20 degrees to 50 degrees of flexion. Decreasing the Q-angle significantly tilted the patella laterally at 20 degrees and from 50 degrees to 80 degrees of flexion, rotated the tibia externally from 30 degrees to 60 degrees of flexion, and increased the tibiofemoral varus orientation from 40 degrees to 90 degrees of flexion. The results show that an increase in the Q-angle could lead to lateral patellar dislocation or increased lateral patellofemoral contact pressures. A Q-angle decrease may not shift the patella medially, but could increase the medial tibiofemoral contact pressure by increasing the varus orientation.

Posterior cruciate ligament injuries: evaluation and management

Posterior cruciate ligament (PCL) injuries commonly occur during sports participation or as a result of motor vehicle accidents. Careful history taking and a comprehensive physical examination are generally sufficient to identify PCL injuries. Most authors recommend nonoperative treatment for acute isolated PCL tears. This involves initial splinting in extension followed by range-of-motion and strengthening exercises. Recovery of quadriceps strength is necessary to compensate for posterior tibial subluxation and to facilitate return to preinjury activity levels. In isolated PCL tears, surgical treatment is reserved for acute bone avulsions and symptomatic chronic high-grade PCL tears. Arthroscopic single-tunnel reconstruction techniques will improve posterior laxity only moderately. Newer double-tunnel and tibial-inlay techniques offer theoretical advantages, but the available clinical results are only preliminary. When a PCL injury occurs in combination with other ligament injuries, most patients will require surgical treatment.

Clinical significance of the arthroscopic drive-through sign in shoulder surgery

PURPOSE

During arthroscopy of the shoulder, the ability to pass the arthroscope easily between the humeral head and the glenoid at the level of the anterior band of the inferior glenohumeral ligament is considered a positive drive-through sign. The drive-through sign has been considered diagnostic of shoulder instability and has been associated with shoulder laxity and with SLAP lesions. The goal of this study was to examine the prevalence of the drive-through sign in patients undergoing shoulder arthroscopy and to determine its relationship to shoulder instability, shoulder laxity, and to SLAP lesions.

TYPE OF STUDY

Case series.

METHODS

We prospectively studied 339 patients undergoing arthroscopy of the shoulder for a variety of diagnosis from 1992 to 1998. The drive-through sign was performed with the patients in a lateral decubitus position and under general anesthesia. The drive-through sign was correlated with preoperative physical findings, intraoperative laxity testing, and with intra-articular pathology at the time of arthroscopy.

RESULTS

The arthroscopic evaluation showed that drive-through sign was positive in 234 (69%) shoulders. For the diagnosis of instability, the drive-through sign had a sensitivity of 92%, a specificity of 37. 6%, a positive predictive value of 29.9%, a negative predictive value of 94.2%, and an overall accuracy of 49%. There was an association between the drive-through sign and increasing shoulder laxity, but not with SLAP lesions.

CONCLUSIONS

This study shows that a positive drive-through sign is not specific for shoulder instability but is associated with shoulder laxity. This arthroscopic sign should be incorporated with other factors when considering the diagnosis of instability.

Olecranon and prepatellar bursitis: treating acute, chronic, and inflamed

Elbow and knee bursitis is common in both athletes and nonathletes and has three basic presentations: acute, chronic nonseptic, and chronic infected. Most acute swellings occur after trauma and can be treated with early aspiration, compression, and padding. Chronic, nonseptic bursitis can usually be treated with conservative therapy and, occasionally, aspiration or corticosteroid injection. Inflamed bursae should be aggressively evaluated and treated. Some may require aspiration and decompression, and oral or intravenous antibiotics should be started to prevent septicemia. Incision and drainage is rarely needed but may be indicated for injuries that do not respond. Surgical excision of the bursa is recommended only for recalcitrant cases.

The value of intercondylar notch visualization of the posteromedial and posterolateral compartments during knee arthroscopy

The intercondylar notch views allow for visualization of the posteromedial and posterolateral compartments of the knee without the use of accessory portals. The purpose of this study was to prospectively evaluate whether these views are useful either diagnostically or therapeutically in the performance of knee arthroscopy. Two surgeons at one institution performed 150 consecutive knee arthroscopies. After arthroscopic examination of the knee using standard portals, a diagnosis and treatment decisions were made. Thereafter, visualization of the posteromedial and posterolateral compartments through the intercondylar notch was undertaken. Each view was performed initially with a 30 degrees arthroscope and 3 questions were asked: (1) Did the view change the diagnosis or add additional information? (2) Did it change the surgical treatment? (3) Was it useful during performance of the procedure? The 70 degrees arthroscope was then used and the same three questions were addressed. In 20.6% of the cases, the intercondylar notch views made a diagnostic and/or therapeutic difference, and the surgical procedure was changed in 11.3% based solely on this information. The views were 3 times as likely to make a difference in anterior cruciate ligament (ACL) reconstructions when compared with arthroscopy without ACL reconstruction (P <.01). The 70 degrees arthroscope added nominal additional information. There were no significant complications. We advocate visualization of the posteromedial and posterolateral compartments through the intercondylar notch as a valuable part of routine knee arthroscopy.

Biomechanical analysis of flat and oblique tibial tubercle osteotomy for recurrent patellar instability

Both flat (Elmslie-Trillat) and oblique (Fulkerson) osteotomy techniques are successful in treating patellar instability episodes by moving the tibial tubercle medially. The oblique osteotomy also results in anterior displacement that decreases patellofemoral forces. Recent reports have described proximal tibial fractures occurring during early weightbearing after oblique osteotomy. We performed oblique and flat osteotomies on 13 pairs of fresh-frozen cadaveric knees. The knees were then tested to failure on a materials testing system by exerting a load through the quadriceps tendon at a rate of 1000 N/sec to simulate a stumble injury. The failure mechanism for flat osteotomies was more likely to be tubercle "shingle" fracture, while oblique osteotomies more frequently failed through a tibial fracture or fixation failure in the posterior tibial cortex. Mean load to failure was significantly higher in the flat osteotomy specimens (1639 N versus 1166 N), as was total energy to failure (224 N.m versus 127 N.m). There was no significant difference in stiffness (87 N/cm versus 74 N/cm). We recommend the flat osteotomy for patients with isolated recurrent patellar instability and the oblique osteotomy in patients who have concomitant patellofemoral pain or articular degenerative changes. When an oblique osteotomy is used, we recommend postoperative brace protection and restricted weightbearing until the osteotomy heals.

Meniscal flounce MR imaging

PURPOSE

To determine the prevalence of a meniscal flounce, the magnetic resonance (MR) imaging characteristics, and whether the flounce is associated with a meniscal tear.

MATERIALS AND METHODS

Knee MR images obtained in 3,159 examinations over 2 years were prospectively evaluated. Ten adult patients (six with true flounces, four with flouncelike folds associated with meniscal tears) with an S-shaped fold in the free edge of a meniscus on sagittal images were included. Five underwent arthroscopic surgery.

RESULTS

The prevalence of a flounce was 0.2% (six of 3,159 examinations). Five occurred in the medial meniscus (MM) and one occurred in the lateral meniscus (LM). All appeared truncated in the coronal plane. Four meniscal tears also demonstrated flouncelike folds. Three were confirmed with surgery and one was confirmed with clinical findings. Of the 3,159 MR examinations, 1,151 demonstrated an MM tear, 832 an LM tear, 542 MM degeneration, and 270 LM degeneration.

CONCLUSION

A meniscal flounce is a fold that occurs in the absence of a tear, and presence of it does not increase the prevalence of a tear. Because tears may result in a flouncelike fold, a flounce should be considered a normal variant only in the absence of other indications of a meniscal tear.

Giant synovial cyst of the shoulder presenting as a chest wall mass

Synovial cysts are most frequently found about the knee. Less commonly they have been described at the shoulder, elbow, ankle, and hip joints. Synovial cysts of the shoulder are associated with rheumatoid arthritis, osteoarthritis, chronic steroid use, Charcot joint disease, and long-standing rotator cuff tears. Although often asymptomatic, patients may present complaining of pain, loss of joint motion, or presence of an unexplained mass. The authors present the case of an elderly man with a very large synovial cyst presenting as an anterior chest wall mass.

Prevention of arthrofibrosis after anterior cruciate ligament reconstruction using the central third patellar tendon autograft

A retrospective analysis was performed to explain the decreasing incidence of postoperative arthrofibrosis of the knee in 191 consecutive patients who had anterior cruciate ligament reconstruction using the central third patellar tendon from 1987 through 1991. Follow-up data were available on 188 patients (98%). Age, sex, time interval from injury, preoperative motion, and concomitant meniscal repair or partial meniscectomy were evaluated for their significance as risk factors. Twenty-two of 188 patients (12%) developed arthrofibrosis; the incidence was lower when the acute anterior cruciate ligament reconstruction was delayed at least 3 weeks from the injury, and when preoperative extension was 10 degrees or better. Age, sex, preoperative flexion, and need for concomitant meniscal surgery were not risk factors. The postoperative motion protocol evolved during the study period. Group 1 patients were braced in 45 degrees of flexion for 1 week before passive extension was allowed. In Group 2, motion was started after 48 hours. Group 3 patients were braced in full extension, with motion starting with 24 hours. With these changes, the incidence dropped from 23% to 3%. Decreases in the incidence of arthrofibrosis with modifications in operative technique and postoperative analgesia were not statistically significant.

The surgical treatment of arthrofibrosis of the knee

Sixty-one lysis of adhesion procedures were performed for arthrofibrosis of the knee between 1981 and 1990. In 43 cases (37 patients) the etiology was prior knee ligament surgery. Ten cases had sustained fractures about the knee and eight had miscellaneous etiologies. Six patients required a second lysis of adhesion procedure. A retrospective analysis of the 43 ligament patients was undertaken to evaluate the results of surgical treatment. All 43 cases were available for followup at an average of 3.6 years. Surgical indications included flexion or extension deficits of > or = 10 degrees or when motion failed to improve despite 2 months of intense therapy. Follow-up assessment included clinical and radiographic evaluation. Flexion improved from 83% to 97% of the contralateral side. Extension deficits improved from 14 degrees to 3 degrees. Only 23 of 37 patients (62%) achieved satisfactory functional results. Radiographic evidence of degenerative changes, soft tissue calcification, and patella infera was found in 89%, 51%, and 9% of the patients, respectively. Patients requiring surgical treatment for arthrofibrosis after knee ligament surgery achieved excellent motion gains, but functional outcome scores were compromised and radiographic findings were concerning. Patients with the localized anterior intraarticular variant or those undergoing lysis of adhesion surgery sooner than 6 months had outcomes comparable with controls.

Osgood-Schlatter's disease complicating anterior cruciate ligament reconstruction

Osgood-Schlatter's disease (OSD) is generally felt to be a benign self-limited disorder. In a small number of patients a symptomatic free bone ossicle persists at the tibial insertion of the patellar tendon. We report the case of a collegiate soccer player with a history of OSD who sustained an acute rupture of his anterior cruciate ligament (ACL). The presence of a free bone ossicle in his patellar tendon necessitated modification of our routine approach to ACL reconstruction. Awareness of the potential for patellar tendon graft problems in patients with previous OSD will allow surgeons to plan alternative reconstructive techniques based on the specific needs of the patient.

Renal histamine increases in the streptozotocin-diabetic rat

Renal histamine concentration, total histamine and protein contents were measured in rats made diabetic via iv streptozotocin injection and held for 13 weeks following diagnosis of diabetes. Insulin (7 U/day) or alpha-hydrazinohistidine (alpha-HH, 25 mg/kg/day) or both drugs were administered to diabetic subgroups the last 2 weeks of the holding period. Untreated diabetics developed significant increases of renal histamine concentration and total histamine content, up 45 and 46%, respectively. Drug interventions reduced the diabetic increases of histamine concentration and content (in order) as follows: diabetic-insulin, down 7 and 8%; diabetic-alpha-HH down 25 and 26%; diabetic-insulin + alpha-HH, down 35 and 36%. Renal tissue protein content was unchanged and qualitative proteinuria was present in all diabetic subgroups. The data indicate that in experimental diabetes there is an increase of the renal inducible histamine pool which is partially reduced by insulin and/or alpha-HH treatments. In view of the long-recognized actions of histamine upon microvascular permeability, elevated renal histamine may be one pathophysiological mediator of the diabetic functional renal microangiopathy manifest as proteinuria.

Changes in plasma histamine concentration in the streptozotocin-diabetic rat

Plasma histamine concentrations were measured in rats made diabetic via jugular vein injection of streptozotocin and held 4 weeks following diabetes diagnosis. At least 15 diabetic animals received insulin (6-8 U/day) or alpha-hydrazinohistidine (alpha-HH) for the last week of the holding period. alpha-HH is a specific inhibitor of histidine decarboxylase (HD), the principle histamine-forming enzyme in mammals. Plasma histamine concentrations, expressed as means and mean standard errors (ng/ml) were as follows: control, 25.5 +/- 2.4; diabetic, 47.1 +/- 5.2; diabetic-insulin, 34.6 +/- 2.9; diabetic-alpha-HH, 28.1 +/- 2.1. These data indicate that in experimental diabetes there is an expansion of the nascent, or inducible histamine pool, an increase which is reflected by increased circulating plasma histamine. This may be one component mediating altered microvessel as well as large vessel permeability characteristics, an underlying component of both diabetic microangiopathy and macroangiopathy.