The anatomy of the posterolateral aspect of the rabbit knee.

The purpose of this study was to determine the anatomy of the posterolateral aspect of the rabbit knee to serve as a basis for future in vitro and in vivo posterolateral knee biomechanical and injury studies. Twelve nonpaired fresh-frozen New Zealand white rabbit knees were dissected to determine the anatomy of the posterolateral corner. The following main structures were consistently identified in the rabbit posterolateral knee: the gastrocnemius muscles, biceps femoris muscle, popliteus muscle and tendon, fibular collateral ligament, posterior capsule, ligament of Wrisberg, and posterior meniscotibial ligament. The fibular collateral ligament was within the joint capsule and attached to the femur at the lateral epicondyle and to the fibula at the midportion of the fibular head. The popliteus muscle attached to the medial edge of the posterior tibia and ascended proximally to give rise to the popliteus tendon, which inserted on the proximal aspect of the popliteal sulcus just anterior to the fibular collateral ligament. The biceps femoris had no attachment to the fibula and attached to the anterior compartment fascia of the leg.This study increased our understanding of these structures and their relationships to comparative anatomy in the human knee. This knowledge of the rabbit's posterolateral knee anatomy is important to understand for biomechanical and surgical studies which utilize the rabbit knee as a model for human posterolateral knee injuries.     

The posterior cruciate ligament and rotatory knee instability. An experimental study

The importance of the posterior cruciate ligament in relation to valgus-varus and axial rotatory stability in the knee joint was investigated. Mobility patterns were drawn from 20 osteoligamentous preparations after successive transection of the posterior cruciate ligament (PCL), the medial and lateral collateral ligaments, and the posterior joint capsule. The knee joint remained grossly stable after isolated transection of the PCL, and further cutting of either one of the collateral ligaments or of the posterior capsule yielded no greater instability than one should expect from isolated cutting of each of these structures. The posterior cruciate ligament was the stabilizing factor in flexion and external rotation after injury to the lateral collateral ligament and the posterolateral capsule, and it restricted internal rotation after cutting of the medial cruciate ligament and the posteromedial capsule. Valgus instability was markedly increased during the whole range of movement when PCL was included in injury to the medial compartment ligaments, and when included in a lateral compartment injury a further varus instability was found, though only in the flexed or semiflexed knee. No hyperextension could be demonstrated after these injuries.     

The direct posterior approach to the knee: surgical and anatomic approach

The direct posterior surgical approach to the knee provides broad exposure of posterior neurovascular structures, the posterior aspect of the femoral condyles and tibial plateau, the posterior joint capsule, and a variety of additional soft-tissue structures including the popliteus, hamstring insertions, and origins of the gastrocnemius. Reported indications for this approach include tumor resection, posterior synovectomy, open reduction and internal fixation of posterior tibial plateau shear fractures, fixation of bone avulsions associated with a posterior cruciate ligament (PCL) injury, repair of posterior vascular injuries, and more recently, posterior inlay PCL reconstructions. However, use of this approach is uncommon and as a result, orthopedic residents and practicing orthopedic surgeons may not be familiar with the appropriate surgical anatomy. This report demonstrates in stepwise fashion the surgical approach and relevant anatomy through a detailed series of fresh cadaveric dissections.     

The subcoracoid space. An anatomic study

Soft tissue impingement under the coracoid process has recently been identified as a cause of painful shoulder disability. In this study the normal space between the humeral head and the coracoid process in two functional positions of the arm was measured in an attempt to delineate anatomic risk factors predisposing to subcoracoid impingement. Forty-seven normal shoulders were studied by computerized tomography (CT) in adduction, 20 additionally in forward flexion/internal rotation, which is the position most frequently causing subcoracoid impingement. The distance between the humeral head and the coracoid tip averaged 8.7 mm for the adducted arm and 6.8 mm for the flexed arm. Modifications of the coracohumeral relationship were found to affect the subcoracoid clearance roughly 1.5 times more in flexion than with arm at the side. Subcoracoid impingement appeared particularly likely during forward flexion of a shoulder with a coracoid tip close to the scapular neck and projecting far laterally.     

枢椎椎板螺钉固定的解剖学研究

目的:测量枢椎椎板和椎弓根的解剖学参数,探讨枢椎后路椎板螺钉固定的可行性。方法:用游标卡尺和量角器测量50例干燥枢椎标本与椎板螺钉进钉技术相关的解剖学数据,指标包括椎板上、中、下部分的厚度,椎板高度,椎弓根高度,椎弓根上、中部宽度,进钉点至椎动脉孔内侧壁及侧块中点的距离,椎板轴线与矢状面的夹角。结果:椎板上部厚度平均为4.34mm;中部厚度平均为6.16mm,16%小于5mm;下部厚度平均为6.15mm,18%小于5mm;椎板高度平均为12.30mm;椎弓根高度平均为8.25mm;椎弓根上部宽平均为7.39mm,16%小于5mm;中部宽平均为5.28mm,22%小于5mm;进钉点至椎动脉孔内侧壁及侧块中点的距离分别平均为32.52mm和28.23mm;椎板轴线与矢状面的夹角平均为43°。结论:枢椎后路椎板螺钉固定在国人是可行的,适用于88%的患者。与枢椎椎弓根螺钉固定相比,椎动脉损伤的危险性小,但其力学性能需进一步探讨。     

Long-term followup of anatomic graduated components posterior cruciate-retaining total knee replacement.

The purpose of the current study was to evaluate the authors' 15-year experience with the Anatomic Graduated Components total knee replacement. This is a report of the survivorship of 4583 Anatomic Graduated Component total knee arthroplasties. Kaplan-Meier survival analyses were performed with the end point defined as radiographic loosening, revision, or both. This end point was subdivided into the best case scenario in which it was assumed that all the patients lost to followup were doing well throughout the study and a worst case scenario in which it was assumed that all patients lost to followup had failed results at their last clinic visit. There were six (0.18%) femoral, 21 (0.46%) tibial, and 180 (4.2%) all-polyethylene patellar component failures secondary to aseptic loosening. All femoral components and 90% of the tibial components were revised; however, only 15 patellar components were revised. The clinical survival rate with revision of one or more of the components was 98.86% at 15 years. Despite having nearly flat-on-flat geometry and retaining the posterior cruciate ligament, which should increase the stresses in the polyethylene and at the bone-cement interface, this total knee replacement has proved to have minimal wear and excellent longevity with time. The authors think this is a result of the direct compression molded polyethylene articulation and the nonmodular configuration that incorporates metal backing on the tibial component and eliminates back-sided tibial component polyethylene wear.     

The posterior branch of the axillary nerve: an anatomic study

BACKGROUND: Surgery on the posterior aspect of the shoulder has become accepted practice for a number of pathological conditions affecting the scapula and the glenohumeral joint. Despite this trend, the anatomy of the posterior branch of the axillary nerve has not been well characterized. The purpose of the present study was to determine the innervation pattern and surgical relationships of the posterior branch of the axillary nerve. METHODS: Nineteen fresh-frozen human cadaveric forequarter amputation specimens were dissected through a posterior approach. The location of the posterior branch of the axillary nerve and its anatomical relationships with surrounding structures were documented and measured with use of digital calipers. RESULTS: The posterior branch separated from the main anterior circumflex branch of the axillary nerve immediately anterior to the origin of the long head of the triceps muscle at the six o'clock position on the glenoid. It coursed posteriorly, adjacent to the inferior aspect of the glenoid rim for an average distance of 10 mm (range, 2 to 17 mm) before dividing into the superior-lateral brachial cutaneous nerve and the nerve to the teres minor. The nerve to the teres minor coursed medially along the posterior aspect of the inferior part of the glenoid rim for an average distance of 18 mm (range, 11 to 25 mm) before entering the muscle at its inferior border. The superior-lateral brachial cutaneous nerve coursed inferiorly, deep to the posterior aspect of the deltoid. It became superficial by passing around the medial border of the muscle at an average of 8.7 cm (range, 6.3 to 10.9 cm) inferior to the posterolateral corner of the acromion. CONCLUSIONS: The posterior branch of the axillary nerve has an intimate association with the inferior aspects of the glenoid and shoulder joint capsule, which may place it at particular risk during capsular plication or thermal shrinkage procedures. The superior-lateral brachial cutaneous nerve and the nerve to the teres minor always arise from the posterior branch. Thus, loss of sensation over the deltoid may indicate loss of teres minor function. The posterior aspect of the deltoid has a more consistent supply from the anterior branch of the axillary nerve, necessitating caution when performing a posterior deltoid-splitting approach to the shoulder.     

Glenoplasty for recurrent posterior shoulder instability. An anatomic reappraisal

Posterior glenoplasty, as performed for the treatment of recurrent posterior shoulder instability, was shown to thrust the humeral head forward and was able to cause symptomatic impingement of the anterior cuff between the coracoid process and the humeral head. Such subcoracoid impingement is relieved by resection of the inferolateral part of the coracoid tip and of the coracoacromial ligament.     

The incidence of rotator cuff rupture. An anatomic study

To evaluate the incidence of rotator cuff ruptures, we examined 122 autopsy specimens of the shoulder and compared our results with those reported in the literature. The incidence of partial tears in our study was 28.7%; the incidence of complete rupture was 30.3%. The frequency increased with age. We found no cuff rupture without supraspinatus tendon involvement. Very often, the cuff tear was bilateral. We do not share the opinion that the rupture of the rotator cuff is primarily an injury of men. We found a higher incidence in female than in male shoulders.     

An anatomic study of transpedicular posterior fixation of spine and its clinical application]

Intact anatomic specimens of spinal column from T8-L5 were obtained and the height and width of vertebral pedicles, the distance between the pedicle to the upper and lower borders of the vertebral body, the angle of inclination of the coronal surface of vertebral pedicles, and other parameters were measured. Simulating pedicle screw implant in operation, K-wires were inserted into the pedicles and after taking X-ray films the pedicles were sectioned transversely. A series of morphologic parameters of the pedicles were obtained. The distances between the two K-wires' entry and exit points, and between the two pedicles of the same or the adjacent vertebra were measured. The relationships of the sites of determining the pedicle screw site was evaluated also from roentgenograms. Twenty two patients of thoracolumbar fracture were treated. The vertebral body height, kyphotic deformity and the displacement were corrected obviously. After operation the neural functions from incomplete paraplegia were recovered. Several problems about the pedicle screw implant technique were discussed.     

枢椎棘突椎板螺钉固定技术及其解剖学研究

目的 明确枢椎后路棘突椎板螺钉固定的可行性和技术参数,为临床应用提供参考.方法 选取20具枢椎标本,仔细解剖以清楚地暴露椎板和棘突.以棘突基底部为进钉点,双侧平行置入棘突椎板螺钉,通过CT重建测量棘突的宽度、螺钉在横断面上的前倾角度、钉道长度及钉尖与脊髓、椎动脉距离.结果 所有螺钉均成功置入,未发现螺钉侵犯椎管、横突孔情况发生.重建CT测量发现棘突椎板螺钉在横断面的前倾角度为76.8°±10.6°;螺钉钉道平均长度为(23.1±3.2)mm,其中上位螺钉钉道长度[(22.9±3.3)mm]稍短于下位螺钉钉道长度[(23.3±3.1)mm],但差异无统计学意义(P＞0.05);螺钉钉尖与脊髓和椎动脉的距离分别为(5.3±1.6)mm和(17.4±3.7)mm.上下位螺钉前倾角度、与椎动脉和脊髓的距离数据略有不同,但差异均无统计学意义(P＞0.05).结论 枢椎棘突椎板螺钉固定具有解剖学可行性,也许可以作为枢椎后路固定的一种补充内固定方法.

Abstract：

Objectives To explore the feasibility and the technical parameters in posterior C2 spinous process laminar screw fixation, and discuss the clinic significance of C2 spinous process laminar screws. Methods Twenty cervical cadaveric spines of C2 were dissected, with care taken to expose the lamina and spinous process. After the entrance point of spinous process screw were determined, posterior C2 spinous process laminar screw implantation was performed under visual control. On the morphologic CT scan,the angle and length of the spinous process laminar screw trajectory and the distance between the tip of the screw and the spinal cord and the vertebral artery were measured. Results The C2 spinous process laminar screws were successfully placed, without impingement of the spinal cord and the vertebral artery. There were little differences between superior and inferior screws in the angle, trajectory length and the distance between the tip of the screw and the spinal cord and the vertebral artery, but without significance (P＞0.05). The placed angles of the screws were 76. 8°± 10. 6° in the axial plane. The distance between the tip of the screw and the spinal cord and the vertebral artery was (5.3+1.6) mm and (17.4 ± 3.7) mm respectively. The trajectory length was (23.1±3.2) mm. Conclusions Posterior C2 spinous process laminar screw fixation is feasible. C2 spinous process laminar screw fixation affords an alternative to standard screw placement for plate fixation and cervical stabilization.     

The female knee: anatomic variations

Traditional knee implants have been designed "down the middle,"based on the combined average size and shape of male and female knee anatomy.Sex-based research in the field of orthopaedics has led to new understanding of the anatomic differences between the sexes and the associated implications for women undergoing total knee arthroplasty. Through the use of a comprehensive bone morphology atlas that utilizes novel three-dimensional computed tomography analysis technology, significant anatomic differences have been documented in the shape and size of female knees compared with male knees. This research identifies three notable anatomic differences in the female population: a less prominent anterior condyle, an increased Q angle, and a reduced medial-lateral:anterior-posterior aspect ratio.     

Development of the olecranon bursa. An anatomic cadaver study

Anatomic dissection of the elbows of 63 cadavers selected at random were performed in an attempt to find out whether the incidental disparity of olecranon bursitis between children and adults might be explained by anatomic differences. The volume of the bursae was determined by syringes used for methylene blue injections. There were no olecranon bursae in children under the age of 7 years; the volume of the bursae increased with age; and the bursa was usually larger on the right, i.e., the common dominant side. The formation of the bursae in late childhood can explain the low incidence of olecranon bursitis in children.     

The anatomic total knee resurfacing arthroplasty

The long-term results of total knee arthroplasty are largely dependent on the degree to which the implants and the technique for their insertion duplicate the normal joint anatomy, mechanics, and kinematics. Aberrations in these modalities, occasioned by technical malalignment of the joint or by nonanatomic designing, sizing, or positioning of the implants, are the predominant causes of postoperative limitation of motion and loosening of the implants. Although inadequacies in the bonding effect of cement and in the structural strength of polyethylene have been cited as contributing factors in the incidence of loosening of the tibial component, this complication occurred in less than 2% of 532 cemented Anatomic Total Knee (ATK) replacements that were available for review at a follow-up period of two to 11 years. The long-term follow-up results, based on pain relief, motion, and level of activity, were judged excellent or good in 89% of the knees. Problems related to the patella and loosening of the tibial component were the predominant mechanical complications that required revision. The incidence of loosening was routinely related to technical malalignment of the knee joint or the prosthesis. However, experimental and recent clinical studies indicate that porous-surfaced implants may provide a more durable and long-lasting mode of stabilization. Except for the adaptation of the implants to the porous-coated, noncemented technique, the ATK arthroplasty ensemble has remained essentially unchanged from the original 1972 design.     

Anatomy of the posterolateral aspect of the goat knee.

The purpose of this study was to determine the anatomy of the posterolateral aspect of the goat knee for future in vivo studies using a goat model to examine the natural history of posterolateral knee injuries. Twelve non-paired, fresh-frozen, adult goat knees were dissected to determine the anatomy of the posterolateral corner. The main posterolateral structures identified in the goat knee were the lateral collateral ligament, the popliteus muscle and tendon, popliteomeniscal fascicles, and the lateral gastrocnemius muscle. The lateral collateral ligament was extra-articular and coursed from its proximal attachment, located posterior and proximal to the lateral epicondyle, to its distal attachment on the lateral aspect of the fused proximal tibiofibula. The popliteus muscle attached to the medial edge of the posterodistal tibia, traveled anterolaterally, became intra-articular at its musculotendinous junction, and attached to the lateral femur just distal to the lateral epicondyle. Distinct popliteomeniscal fascicles attached the lateral meniscus to the popliteus muscle and tendon, and a fascial attachment from the musculotendinous junction of the popliteus muscle coursed to the lateral tibial plateau. This study provided information on the structures present in the posterolateral aspect of the goat knee and enhanced our understanding of their relationships to analogous structures in the human knee. This information is important to enable future development of potential models of the natural history of posterolateral knee injuries and also to test surgical techniques and the in vivo effects of these injuries on cruciate ligament reconstructions.