Articular cartilage injuries of the knee: evaluation and treatment options.

Articular cartilage defects of the knee can be very debilitating, and diagnosis can be difficult because the symptoms are often nonspecific. Routine MRI scans, despite vast improvement in detection techniques, are often not sensitive or specific enough, especially for low-grade lesions. Therefore, articular cartilage injuries of the knee are often a diagnosis of exclusion requiring a thorough history, a good physical exam, and a high index of suspicion. Treatment of these injuries is still evolving, but new treatment options, including autogenous chondrocyte implantation, look promising, and long-term outcomes, while not yet complete, look encouraging.

Cervical spine alignment in the immobilized ice hockey player. A computed tomographic analysis of the effects of helmet removal.

To determine if helmet removal causes a significant increase in lordosis of the cervical spine in ice hockey players, we radiographically assessed the position of the cervical spine in subjects immobilized to a standard spine backboard wearing shoulder pads both with and without a helmet. Ten adult male volunteers (ages, 18 to 28 years) with no previous history of cervical spine injuries were fitted with an appropriately sized ice hockey helmet and shoulder pads and immobilized in a supine position to a standard spine backboard. Computerized tomographic lateral scout scans were obtained of the cervical spine for three conditions: 1) no equipment (control), 2) helmet and shoulder pads, and 3) shoulder pads only (helmet removed). With the helmet removed and the shoulder pads remaining, a significant increase in C2 to C7 lordosis was found when compared with the other two conditions. Individual segmental measurements revealed a significant increase in cervical lordosis at the C6-7 level with the helmet removed compared with the helmet and shoulder pads condition. Our results demonstrate that the removal of an ice hockey helmet from a supine player causes a significant increase in lordosis (extension) of the cervical spine. We recommend that ice hockey helmets not be removed from injured players, with rare exceptions, because doing so results in unnecessary motion of the cervical spine.

Torsional rigidity of scoliosis constructs.

STUDY DESIGN: A biomechanical study of the rigidity of various scoliosis constructs instrumented with and without caudal pedicle screw anchors and with none, one, or two cross-link devices. OBJECTIVES: To determine whether the increased torsional rigidity provided by distal pedicle screw fixation might make cross-linking unnecessary. SUMMARY OF BACKGROUND DATA: Pedicle screws and cross-linking devices have been shown to increase the structural rigidity of spinal constructs. Their relative contributions to scoliosis construct rigidity has not been determined. METHODS: "Short" (T2-T11) and "long" (T2-L3) scoliosis constructs were mounted on an industrially fabricated spine model and tested in a hydraulic testing machine. Four different short and four different long constructs were tested: hooks only, hooks with concave side thoracic sublaminar wires, hooks with distal pedicle screw anchors, and hooks, distal pedicle screw anchors, and concave thoracic sublaminar wires. There were four iterations for each construct tested: no cross-links, one superior cross-link at T4-T5, one inferior cross-link at T9-T10, and two cross-links. Torsional rigidity was tested by applying a rotational torque at T2. Vertebral body motion was recorded with a three-dimensional video analysis system. RESULTS: Constructs with distal pedicle screws were statistically more rigid in torsion than those with hooks as distal anchors. The additional torsional rigidity from one or more cross-links was negligible compared with that provided by pedicle screws. CONCLUSIONS: With pedicle screws as distal anchors in scoliosis constructs, cross-linking with one or two devices adds very little additional rotational stiffness and may be unnecessary in many cases.

The magnetic resonance imaging appearance of individual structures of the posterolateral knee. A prospective study of normal knees and knees with surgically verified grade III injuries.

The purpose of this study was to contrast the magnetic resonance imaging appearance of uninjured components of the posterolateral knee with that of injured structures, and to assess the accuracy of magnetic resonance imaging in identifying posterolateral knee complex injuries. Thin-slice coronal oblique T1-weighted images through the entire fibular head were used to identify the posterolateral structures in seven uninjured knees. The appearance of corresponding grade III injuries to these structures was identified prospectively in 20 patients and verified at the time of surgical reconstruction. The sensitivity, specificity, and accuracy of imaging for the most frequently injured posterolateral knee structures in this series were as follows: iliotibial band-deep layer (91.7%, 100%, and 95%), short head of the biceps femoris-direct arm (81.3%, 100%, and 85%), short head of the biceps femoris-anterior arm (92.9%, 100%, and 95%), midthird lateral capsular ligament-meniscotibial (93.8%, 100%, and 95%), fibular collateral ligament (94.4%, 100%, and 95%), popliteus origin on femur (93.3%, 80%, and 90%), popliteofibular ligament (68.8%, 66.7%, and 68%), and the fabellofibular ligament (85.7%, 85.7%, and 85.7%). Magnetic resonance imaging of the knee was accurate in the identification of these injuries.

The supination effect of tendon transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis or longus: a cadaveric study.

Flexor carpi ulnaris (FCU) transfer to the extensor carpi radialis brevis (ECRB) and/or the extensor carpi radialis longus (ECRL) has been commonly used to provide wrist extension. The ability of this wrist extension transfer to also provide forearm supination has been inferred but not formally investigated. This laboratory study investigated the forearm supination effect of FCU transfer to the ECRB and to the ECRL in a cadaveric model. Two vectors of pull were investigated: freeing either the distal one third or the distal two thirds of the FCU ulnar origin. Five fresh-frozen, above-elbow, non-matched cadaveric specimens placed in a mounting device that allowed the arm to rotate about its ulnar axis starting from a full pronated position were measured for resultant supination after tendon transfer and loading. This study showed that the transfer of the FCU into either the ECRB or the ECRL resulted in no significant difference in maximum supination. The vector of origin, however, did significantly affect the maximum supination obtained. Releasing the distal two thirds of the FCU ulnar origin resulted in a mean supination that was significantly greater than the mean supination achieved with releasing the distal one third of the FCU ulnar origin. We concluded that in the cadaveric model, transfer of the FCU into either the ECRB or ECRL provided similar resultant supination and that freeing the distal two thirds of the FCU ulnar origin provided significantly more supination than freeing only the distal one third. For the hand surgeon treating wrist flexion in combination with forearm pronation deformity, transfer of the FCU into the ECRB and/or the ECRL can be used to concomitantly provide wrist extension and forearm supination.

The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force. A biomechanical analysis.

To determine if untreated grade III injuries of the posterolateral structures contribute to increased force on an anterior cruciate ligament graft, we measured the force in the graft in cadaveric knees during joint loading after reconstruction with otherwise intact structures and in the same reconstructed knees after selected cutting of specific posterolateral knee structures. Tests were first performed on the knee with the posterolateral structures intact and then after sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon. The graft force was significantly higher after fibular collateral ligament transection during varus loading at both 0 degree and 30 degrees of knee flexion than it was for the same loading of the joint with intact posterolateral structures. In addition, coupled loading of varus and internal rotation moments at 0 degree and 30 degrees of flexion further increased graft force beyond that with varus force alone. The increase in graft force remained significant with additional sequential cutting of the popliteofibular ligament and popliteus tendon. We believe this study supports the clinical observation that untreated grade III posterolateral structure injuries contribute to anterior cruciate ligament graft failure by allowing higher forces to stress the graft.

Acute Knee Injuries; On-the-Field and Sideline Evaluation.

An athlete who has an acute knee injury should be assessed rapidly on the field and then more thoroughly on the sideline or in the training room. On-the-field assessment includes questions about the mechanism of injury and any similar previous injuries, a visual check for knee deformities and skin injuries, a neurovascular exam, and, ideally, tests for flexion and hyperextension. On the sideline or in the training room, standard physical tests are likely to reveal any significant injuries. These include the patellar apprehension, Lachman, posterior sag, quadriceps active, posterior drawer, posterolateral drawer, valgus and varus stress, pivot-shift, and dial tests.

In vivo kinematics of the rabbit knee in unstable models of osteoarthrosis.

The effects of osteoarthrosis inducing surgery on the kinematics of the rabbit knee were evaluated in vivo. A video motion analysis system was used to track reflective markers attached to two pins fixed in both femur and tibia, and from these data knee kinematics were computed. The control for all measurements was the gait after pins were implanted, but the knee was unaltered. Both a release of the anterior cruciate ligament and a partial medial meniscectomy were then performed, and the animals' gait was recorded at 4, 8 and 12 weeks after knee surgery. Knee kinematics were described by three translations and three rotations and were analyzed in terms of maximum and minimum values and range of motion. Statistical comparisons of these data between control and operated knees were made using Wilcoxon's signed rank test. Results showed an initial increase in maximum anterior displacement which returned to normal after 12 weeks. In addition there was a persistent increase in knee adduction and an increase in the minimum value of external rotation over the 12 week period. At 12 weeks after surgery there was no change in range of any measurable kinematic parameter. Overall, the changes in joint kinematics following partial medial meniscectomy and release of the anterior cruciate ligament were small, suggesting that altered joint kinematics might not be a critical factor in the development of osteoarthrosis in this animal model.

The reharvested central third of the patellar tendon. A histologic and biomechanical analysis.

We assessed the histologic, mechanical, and structural properties of the reharvested central-third patellar tendon in greyhounds. Twelve dogs had the central third of the patellar tendon (5 mm) removed with corresponding bone blocks from the patella and tibia; the remaining tendon defect was loosely closed. Six dogs were sacrificed at 6 months and six at 12 months, and the central third of the patellar tendon was harvested from both the operative and the contralateral control knees. Analysis of the structural changes in the tendons revealed a significant increase in thickness for reharvested tendons at both 6 and 12 months when compared with controls. The entire residual tendons were narrower at 6 months and were shorter at 12 months compared with controls. Mechanical testing showed that the average failure load, ultimate tensile strength, strain at failure, and average modulus for the reharvested central third of the patellar tendon were significantly less than that of controls at both 6 and 12 months. Analysis of collagen fiber size by electron microscopy revealed a significant increase in collagen fiber diameter at 6 months (135 +/- 41 nm versus 49 +/- 4 nm) but no difference between the operative limbs and controls at 12 months. The reharvested bone-patellar tendon-bone complex does not have the same properties as the primary patellar tendon graft up to 1 year after harvest in a canine model, and its use for revision cruciate ligament reconstruction must be carefully reexamined.