Biomechanical stability of an arthroscopic anterior capsular shift and suture anchor repair in anterior shoulder instability: a human cadaveric shoulder model.

It was hypothesized that an arthroscopic Bankart repair with suture anchors supplies sufficient anterior shoulder stability, which cannot be improved by an additional capsular shift. In an experimental biomechanical human cadaver study, we tested ten fresh human cadaver shoulders in a robot-assisted shoulder simulator. External rotation and glenohumeral translation were measured at 0 degrees and 80 degrees of glenohumeral abduction. All measurements were performed under the following conditions: on the non-operated shoulder; following the setting of three arthroscopic portals; following an arthroscopic anterior capsular shift; following a simulated Bankart lesion; and following an arthroscopic Bankart repair. The application of three arthroscopic portals resulted in a significant increase of the anterior (P = 0.01) and antero-inferior translation (P = 0.03) at 0 degrees and 80 degrees abduction, as well as an increase in external rotation at 80 degrees abduction (P = 0.03). Capsular shift reduced external rotation (P = 0.03), but did not significantly decrease translation. Simulating anterior shoulder instability, glenohumeral translation significantly increased, ranging from 50 to 279% of physiological translation. Arthroscopic shoulder stabilization resulted in a decrease of translation in all tested directions to approximately physiologic levels. External rotation in 0 degrees abduction was thus decreased significantly (P = 0.003) to an average of 19 degrees . The study proved that an arthroscopic anterior capsular shift in a cadaveric model decreases external rotation without a significant influence on glenohumeral translation. Arthroscopic shoulder stabilization with suture anchors thus sufficiently restores increased glenohumeral translation, but also decreases external rotation in neutral abduction. An anatomic reconstruction of the Bankart lesion without overconstraining of the antero-inferior capsule should therefore be the aim in arthroscopic anterior shoulder stabilization.

Influence of an infrapatellar fat pad edema on patellofemoral biomechanics and knee kinematics: a possible relation to the anterior knee pain syndrome.

INTRODUCTION: An edema of the infrapatellar fat pad following knee arthroscopy or in case of chronic anterior knee pain syndrome is suspected to increase the patellofemoral pressure by a modification of the patellofemoral glide mechanism. The study was performed to evaluate this hypothesis. MATERIALS AND METHODS: Isokinetic knee extension from 120 degrees of flexion to full extension was simulated on 10 human knee cadaver specimens (six males, four females, average age at death 42 years) using a knee kinemator. Joint kinematics was evaluated by ultrasound sensors (CMS 100, Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-Scan 4000, Tekscan, Boston). Infrapatellar tissue pressure was analyzed using a closed sensor cell which was implanted inside the fat pad (GISMA, Buggingen, Germany). An inflatable fluid cell was implanted by ultrasound control in the center of the infrapatellar fat pad and filled subsequently with water to simulate a fat pad edema. All parameters were recorded and analyzed from 0 to 5 ml volume of the fluid cell. RESULTS: Simulating a fat pad edema resulted in a significant (P < 0.01) increase of the infrapatellar fat pad pressure (247 mbar at 0 ml to 615 mbar at 5 ml volume). In knee extension and flexion the patella flexion (sagittal plane) was decreased while we did not find any other significant influence of the edema on knee kinematics. During the analysis of the patellofemoral biomechanics, a simulated fat pad edema resulted in a significant (P < 0.05) decrease of the patellofemoral force between 120 degrees of knee flexion and full extension. The contact area was reduced significantly near extension (0 degree-30 degrees) by an average of 10% while the contact pressure was reduced at the entire range of motion up to 20%. CONCLUSION: An edema of the infrapatellar fat pad does not cause an increase of the patellofemoral pressure or a significant alteration of the patellofemoral glide mechanism. Anterior knee pain in case of a fat pad edema may be related to a significant increase of the tissue pressure and possible histochemical reactions.

[Modified technique of trapezius transfer to improve function in brachial plexus palsy]. / Modifizierte Technik der Verpflanzung des Musculus trapezius zur Funktionsverbesserung bei Armplexusschäden.

OBJECTIVE: Increase of shoulder stability. Elimination of inferior subluxation of the humeral head. Increase of active abduction. Better control of the paralyzed arm. Decrease or elimination of shoulder pain. INDICATIONS: Palsy of deltoid and supraspinatus muscles with weak abduction, multidirectional shoulder instability and subluxation of the humeral head after complete neurosurgical therapy (neurolysis, reconstruction of the brachial plexus). No essential active function of the elbow and hand. CONTRAINDICATIONS: Weakness of trapezius muscle. Incomplete rehabilitation after neurosurgical procedure. Stiffness of the glenohumeral joint. Arthritis of the glenohumeral joint. SURGICAL TECHNIQUE: The cranial part of the trapezius muscle is detached from the scapular spine and the clavicle. Its insertion at the acromion is left untouched. The acromion is freed from the scapular spine and the lateral end of the clavicle by oblique osteotomies and then transferred to the proximal humerus. Under maximum tension the deltoid muscle is sutured on top of the trapezius muscle. POSTOPERATIVE MANAGEMENT: Immobilization of the arm in an abduction support (75 degrees of abduction) for 6 weeks. The physiotherapy program starts on the 1st postoperative day with assisted and active training of elbow, hand, and fingers. During the 1st postoperative week, the abduction support is removed for physiotherapy, abduction is maintained during the exercises. After 6 weeks, progressive adduction to remove the abduction support is commenced. RESULTS: The procedure was performed in 104 cases. 80 patients were followed up on average after 2.4 years (0.8-8 years). In all cases, the transfer resulted in an increase of function and in 95% in a decrease of multidirectional shoulder instability. The modification of the original technique in the latest 22 cases was superior in terms of shoulder stability. In all these cases, a decrease of instability was achieved and inferior subluxation was abolished.

[External rotation osteotomy of the humerus for treatment of external rotation deficit in palsies]. / Aussenrotationsosteotomie des Humerus zur Behandlung des lähmungsbedingten Aussenrotationsdefizits der Schulter.

OBJECTIVE: Aim of the procedure is shifting the arc of shoulder rotation for an improved external rotation, reaching a physiological elbow flexion without striking of the lower arm against the thorax; improvement of the activities of daily living because guidance of the hand to the face is possible without any simultaneous evasive movements of the shoulder. INDICATIONS: Palsy of infraspinatus and teres minor muscles after complete neurosurgical therapy (neurolysis, reconstruction of the brachial plexus), which leads to loss of external rotation and an internally rotating posture of the arm. Elbow flexion is hindered because of striking of the lower arm against the thorax, simultaneous abduction and foreward flexion is necessary to guide the hand to the face. CONTRAINDICATIONS: Not completed rehabilitation after a neurosurgical procedure. Stiffness of the glenohumeral joint with insufficient passive overall rotational sector due to additional reduced internal rotation. SURGICAL TECHNIQUE: To improve external rotation by shifting of the arc of rotation, a transverse osteotomy is done in the mid third of the humerus and the distal part of the humerus is rotated outward (30-60 degrees ). A dynamic compression plate is used for osteosynthesis. POSTOPERATIVE MANAGEMENT: Immobilization of the arm in a Gilchrist bandage is necessary for 6 weeks (especially at night). The physiotherapy program starts on the 1st postoperative day with assisted and active training of elbow, hand, and fingers, as well as active external rotation of the shoulder. After 6 weeks, all movements and daily activities are allowed. RESULTS: The procedure was performed in 15 cases, followed up on average after 3 years (0.5-8.7 years). In all cases, the shifted arc of rotation (preoperative 37 degrees deficit of external rotation, postoperative 46 degrees increase) eliminated striking of the lower arm against the thorax on flexion of the elbow. All patients were able to guide their hands to their faces without any simultaneous evasive movements of the shoulder.

Dynamic measurement of patellofemoral contact pressure following reconstruction of the medial patellofemoral ligament: an in vitro study.

BACKGROUND: Surgical reconstruction of the medial patellofemoral ligament used to stabilize the patella against lateral dislocation may concomitantly produce alteration of the patellofemoral contact pressure distribution. Two different tendon transfer techniques of reconstructing the medial patellofemoral ligament, one dynamic and one static, as well as a proximal soft tissue realignment of the patella were investigated. METHODS: Eight human knee specimens were mounted in a kinematic knee simulator and isokinetic extension motion was simulated. Patellofemoral pressure was measured using a pressure sensitive film while a 100 N laterally directed dislocation load was applied to the patella. The specimens were evaluated in a physiologic state, as well as after dynamic reconstruction of the medial patellofemoral ligament using a distal transfer of the semitendinosus tendon, following static reconstruction using a semitendinosus autograft, and following proximal soft tissue realignment of the patella. FINDINGS: Following both reconstruction techniques of the medial patellofemoral ligament patellofemoral contact pressure was not significantly (P=0.49) altered. In contrast, after proximal realignment a trend (P=0.07) towards higher contact pressure near knee extension was observed. In the absence of a lateral dislocation load dynamic and static reconstruction resulted in a medialization (P=0.04) of the center of pressure, whereas under the application of a 100 N dislocation load the center of pressure showed no significant alteration. Following proximal realignment the center of pressure was significantly medialized without (P<0.01) and with a dislocation load (P=0.01) throughout the entire range of knee motion. INTERPRETATION: Static and dynamic ligament reconstruction of the medial patellofemoral ligament did not alter patellofemoral pressure. Proximal realignment, on the other hand, resulted in a constant medialization of the patellofemoral pressure. The data suggest that the reconstruction techniques would be associated with a low risk of causing premature cartilage degeneration due to excessive patellofemoral contact pressure, whereas proximal realignment could cause medial overload of the patellofemoral joint.

[Reconstruction of the medial patellofemoral ligament by tunnel transfer of the semitendinosus tendon]. / Die Rekonstruktion des medialen patellofemoralen Ligaments mit der getunnelten Semitendinosussehne.

OBJECTIVE: Stabilization of the patella by reconstruction of the medial patellofemoral ligament. INDICATIONS: Chronic recurrent lateral dislocation or subluxation of the patella. Habitual lateral dislocation of the patella. CONTRAINDICATIONS: Primary dislocation of the patella. Genu valgum with a Q-angle > 15 degrees . Status following semitendinosus tendon transfer to reconstruct the anterior cruciate ligament. Joint infection. Neurogenic instability, ischiocrural muscle deficiency. SURGICAL TECHNIQUE: Division of the distal insertion of the semitendinosus muscle at the pes anserinus. Subligamentous tunneling at the proximal insertion of the medial collateral ligament. The distal end of the semitendinosus tendon is transferred through the subligamentous tunnel to the medial patellar margin. Fixation of the tendon to the medioproximal patellar margin by passing it through an oblique transpatellar drill hole. RESULTS: The patella was stabilized by dynamic reconstruction of the medial patellofemoral ligament in 14 patients with chronic recurrent or habitual lateral patellar dislocation. Ten patients were available for clinical follow-up assessment at an average of 13 months (8-27 months) postoperatively. The postoperative Kujala Index (maximum 100 points) increased on average from 56 to 95 points.

Long term results of bone-patella-tendon-bone ACL reconstruction.

BACKGROUND: To assess outcomes of bone-patella-tendon-bone ACL-reconstruction at 18 years follow-up. MATERIAL AND METHODS: Outcome measures included the IKDC clinical examination form and clinical scores. Radiographs were analyzed to determine the grade of osteoarthritis. RESULTS: 69% of the examined patients (n = 54) had a normal/nearly normal knee, 14% were abnormal and 17% severely abnormal with significant improvement (P ≤ 0.001). The mean Lysholm score was 87.7 ± 12.4 and the Tegner activity level was 5 ± 2. Osteoarthritic changes were present in 52%. CONCLUSION: BPTB ACL-reconstruction provides a satisfactory outcome with a high incidence of radiographic osteoarthritic changes.

[Arthroscopic meniscal repair with bioresorbable implants].

OBJECTIVE: Restoration of the shape and function of a torn meniscus. INDICATIONS: Complete or large incomplete longitudinal tear of the medial and lateral meniscus close to the base, large flap tear, so-called bucket-handle tear. CONTRAINDICATIONS: Degenerative meniscal tissue. Unstable knee joint without concomitant surgical stabilization. Complex meniscal tear or radial tear. Tear in the central avascular region. Gonarthrosis. Joint infection. Local skin disorders. SURGICAL TECHNIQUE: Visualization of the meniscal tear and revitalization of the tear margins with a meniscal rasp or shaver. Introduction of the implant using the surgical technique required and repair of the tear. Percutaneous trepanation of the meniscal base ("needling") to improve healing. POSTOPERATIVE MANAGEMENT: Full weight bearing only with the knee joint extended in an orthosis until after the 6th postoperative week. Knee flexion up to 30 degrees without weight bearing for the first 2 postoperative weeks with physiotherapy, then up to 60 degrees for another 4 weeks. Short movable knee orthosis with 0-0-90 degrees in the 7th-12th postoperative week. After the 12th postoperative week, continuation of physiotherapy without orthosis, until range of movement has been achieved and the knee-stabilizing muscles have regained their strength. Full sporting capacity after 6 months. RESULTS: The healing rate for meniscal repair with bioresorbable implants is between 86% and 95% and is comparable with the average healing rate for open (84-88%) or arthroscopic suture techniques (98%). Between July 1999 and June 2001, a meniscal tear was treated with Clearfix screws in 65 patients. 60 patients (92%) had a follow-up examination on average 18 months postoperatively. Six patients underwent further arthroscopic surgery as a result of pain (four times healed, twice not healed). Another three patients complained of pain on weight bearing at the follow-up examination and had clinically positive meniscus signs. These patients were then evaluated as "treatment failures". The clinical healing rate was therefore 92% (55 out of 60).

Biomechanical and kinematic influences of a total infrapatellar fat pad resection on the knee.

BACKGROUND: This biomechanical study was performed to evaluate the consequences of total infrapatellar fat pad resection on knee kinematics and patellar contact pressure. HYPOTHESIS: Resection of the infrapatellar fat pad produces significant changes in knee kinematics and patellar contact pressure. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Isokinetic knee extension was simulated on 10 human knee cadaveric specimens (6 men, 4 women; mean age at death, 44 years). Joint kinematics were evaluated by an ultrasound-based 3D motion analysis system, and retro-patellar contact pressure was measured using an electronic pressure-sensitive film. All data were taken before and after resection of the infrapatellar fat pad and statistically analyzed. RESULTS: A total resection of the infrapatellar fat pad resulted in a significant decrease of the tibial external rotation relative to the femur between 63 degrees of flexion and full knee extension (maximum: 3 degrees rotation difference at 0 degrees knee flexion, P = .011), combined with a significant medial translation of the patella between 29 degrees and 69 degrees of knee flexion (range, 0.9-1.3 mm, P = .017-.028). Retro-patellar contact pressure was significantly reduced (from 20% to 25%, P = .008-.021) at all flexion angles. CONCLUSION: A resection of the infrapatellar fat influences patellar biomechanics and knee kinematics. CLINICAL RELEVANCE: The infrapatellar fat pad may have a biomechanical function and may play a role in anterior knee pain syndrome.

Biomechanical properties of commonly used autogenous transplants in the surgical treatment of chronic lateral ankle instability.

The purpose of this study was to evaluate the biomechanical properties of commonly used autogenous transplants for the surgical stabilization of chronic lateral ankle instability. We dissected the transplants (peroneus longus, peroneus brevis, Achilles and plantaris tendon, periosteal flap, fascia, corium) and the anterior talofibular ligament from 13 fresh anatomic specimens. After laser-assisted measurement of the transplant diameter, we assessed their biomechanical properties with a universal testing device. Biomechanical stability of the peroneus longus, peroneus brevis, and Achilles tendons was significantly higher than the other transplants. The stability parameters of the periosteal flap were in the range of the anterior talofibular ligament but inferior to the tendons. The application of a transplant with low biomechanical stability, such as the periostal flap, requires more postoperative immobilization as in a strong orthosis or cast.

Risk evaluation of thermal injury to the cervical spine during intradiscal laser application in vitro.

OBJECTIVE: We aimed to investigate temperature distribution during laser and its possible thermal damage to the neurovascular structures. BACKGROUND DATA: Percutaneous laser disc decompression (PLDD) is now being performed as a minimally invasive intradiscal technique for the operative therapy of non-sequestered herniated cervical discs. As yet, no experimental basic research has been reported with regard to temperature rise and distribution in the cervical region during laser radiation. MATERIALS AND METHODS: An in vitro laser procedure was performed on human cervical intervertebral discs under standardized conditions. A thermo-camera was used to monitor in real-time the zones sensitive to temperature increase. RESULTS: Average intervertebral disc volume was 2000 mm3. With a total energy conduction of 600 Joules, a temperature increase of around 30 degrees C was shown with an initial temperature of 28 degrees C at the posterior longitudinal ligament lying immediately in front of the myelon. The defect volume was less than 1% of the total intervertebral disc volume. CONCLUSION: If, during laser application, the total amount of conducted energy is too high, with an unfavorable position of the fibers in the intervertebral space, there is a risk of thermal damage to the spinal cord and nerve roots.

Reconstructive operations for the upper limb after brachial plexus palsy.

Limited function due to paralysis following brachial plexus lesions can be improved by secondary operations of the bony and soft tissue. Between April 1994 and December 2000, 109 patients suffering from arm-plexus lesions underwent a total of 144 reconstructive operations guided by our concept of integrated therapy. The average age at the time of surgery was 32 years (range: 15-59). The following operations were performed: shoulder arthrodesis (23), trapezius transfer (74), rotation osteotomy of humerus (9), triceps to biceps transposition (9), transposition of forearm flexors or extensors (8), latissimus transfer (7), pectoralis transfer (1), teres major transfer (1), transposition of flexor carpi ulnaris to the tendons of extensor digitorum (10), and wrist arthrodesis (2). Prospectively, in all patients, the grade of muscle power of the affected upper extremity was evaluated prior to surgery. The follow-up period for all 144 operations was, on average, 22 months (range: 6-74). By means of operative measures, almost all patients obtained an improvement of shoulder function (100%) and stability (>90%), elbow flexion (85%), and hand, finger, and thumb (100%). When muscles malfunction after brachial plexus lesions, one should take into account the individual neuromuscular defect, passive joint function, and bony deformities; different procedures such as muscle transpositions, arthrodeses, and corrective osteotomies can then be performed to improve function of the upper extremity. Each form of operative treatment presents patients with certain benefits and all are integrated into a total treatment plan for the affected extremity.

Biomechanical effectiveness of an arthroscopic posterior bankart repair versus an open bone block procedure for posterior shoulder instability.

BACKGROUND: The most effective surgical treatment for traumatic posterior shoulder instability remains unclear. HYPOTHESIS: An arthroscopic posterior Bankart repair is as effective as an open posterior bone block-capsulorrhaphy procedure regarding the restoration of humeral displacement with posterior and inferior forces. STUDY DESIGN: Controlled laboratory study. METHODS: Biomechanical testing of 16 human shoulders was performed in 3 testing conditions: after ventilation (intact joint), after creation of a posteroinferior Bankart lesion with an additional cut of the posterior band of the inferior glenohumeral ligament, and after surgical shoulder stabilization. The shoulder stabilization was performed either by an open posterior bone block procedure and glenoid-based T-capsulorrhaphy or by an arthroscopic Bankart repair. Testing was performed in 2 positions-the sulcus test position and the jerk test position-with a passive humerus load of 50 N applied in the posterior, posteroinferior, and inferior directions. RESULTS: After the arthroscopic repair, there was no significant difference between the translation and the intact state for all tested directions. The bone block repair-capsulorrhaphy caused a significant decrease of posterior translation (sulcus test and jerk test positions) and posteroinferior translation (jerk test position). But the resulting posterior and posteroinferior translation was even significantly lower than the translation measured for the intact joints. However, the reduction of inferior translation, compared with that of the defect condition, was not significant after the bone block repair (sulcus test and jerk test positions). Compared with that of the intact joint, inferior translation after the bone block repair was significantly higher. CONCLUSION: The posterior bone block repair-capsulorrhaphy overcorrects posterior translation and does not effectively restore inferior stability, whereas the arthroscopic posterior Bankart repair restores posterior and inferior laxity of the intact joint. CLINICAL RELEVANCE: An arthroscopic posterior capsulolabral repair more precisely restores posterior and inferior glenohumeral joint laxity and is therefore recommended as the first choice of treatment.

A rotating inlay decreases contact pressure on inlay post after posterior cruciate substituting total knee arthroplasty.

BACKGROUND: The post/cam mechanism of posterior cruciate substituting total knee arthroplasty, which is intended to achieve maximum range of flexion, offers the risk of failure due to mechanical overload. The purpose of this in vitro study was to investigate load and contact pressure on the inlay post of posterior substituting knee prosthesis with different designs. METHODS: Isokinetic extension/flexion motions of seven fresh frozen left knee specimens were simulated dynamically in a specially designed knee simulator with an extension moment of 31 Nm. After implantation of the knee prosthesis system, which provides a fixed and a rotating posterior cruciate substituting inlay, a pressure sensitive film was fixed on the inlay post surface to measure maximum load and contact pressure. FINDINGS: Both types of inlays showed nearly the same contact load of up to 480 N on the posterior surface of the inlay post at 120 degrees knee flexion. Contact pressure was measured to be up to 19.7 MPa at 120 degrees flexion on the posterior surface of the post of the fixed inlay, whereas contact pressure was measured to be significantly lower (6.8 MPa, p=0.04) on the inlay post of the rotating inlay. INTERPRETATION: The modification of a rotating posterior cruciate substituting inlay could not decrease the horizontal load, but offers the possibility to decrease contact pressure on the inlay post to avoid mechanical overload of the polyethylene inlay.

The influence of patellar bracing on patellar and knee load-distribution and kinematics: an experimental cadaver study.

The aim of this study was to analyze the biomechanical consequences of patella bracing in order to evaluate possible mechanisms supporting its clinical application. The hypothesis is that the patellar bracing reduces patellofemoral pressure by influencing patellar and knee kinematics, and load distribution. Physiologic isokinetic knee extension motions were simulated on ten human knee cadaver specimens using a knee kinematic simulator. Joint kinematics were evaluated using an ultrasound-based motion analysis system and patellofemoral contact pressure was measured using a thin-film piezoresistive pressure measuring system. Infrapatellar tissue pressure was analyzed using a closed sensor-cell. Three different patella braces were fitted to the knee cadavers and their influence on the kinematic and kinetic biomechanical parameters were evaluated and compared to the physiologic situation. Patellar bracing resulted in a significant (p = 0.05) proximalization of the patella up to 3 mm. Depending on the type of brace used, a decrease in the infrapatellar fat pad pressure was found and the patellofemoral contact area was decreased significantly (p = 0.05) between 60 degrees of knee flexion and full extension (maximum 22%). Patella bracing significantly (p = 0.05) reduced the patellofemoral contact pressure an average of 10%, as well as the peak contact pressure which occurred. Patellar bracing significantly influences patella biomechanics in a reduction of the patellofemoral contact area and contact pressure as well as a decrease in the infrapatellar tissue pressure. The application of infrapatellar straps is suggested for the treatment and prevention of anterior knee pain, especially in high level sports.

Characterized chondrocyte implantation results in better structural repair when treating symptomatic cartilage defects of the knee in a randomized controlled trial versus microfracture.

BACKGROUND: As the natural healing capacity of damaged articular cartilage is poor, joint surface injuries are a prime target for regenerative medicine. Characterized chondrocyte implantation uses an autologous cartilage cell therapy product that has been optimized for its biological potency to form stable cartilage tissue in vivo. PURPOSE: To determine whether, in symptomatic cartilage defects of the femoral condyle, structural regeneration with characterized chondrocyte implantation is superior to repair with microfracture. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Characterized chondrocyte implantation was compared with microfracture in patients with single grade III to IV symptomatic cartilage defects of the femoral condyles in a multicenter trial. Patients aged 18 to 50 years were randomized to characterized chondrocyte implantation (n = 57) or microfracture (n = 61). Structural repair was blindly assessed in biopsy specimens taken at 1 year using (1) computerized histomorphometry and (2) evaluation of overall histological components of structural repair. Clinical outcome was measured using the self administered Knee injury and Osteoarthritis Outcome Score. Adverse events were recorded throughout the study. RESULTS: Characterized chondrocyte implantation resulted in better structural repair, as assessed by histomorphometry (P = .003) and overall histologic evaluation (P = .012). Aspects of structural repair relating to chondrocyte phenotype and tissue structure were superior with characterized chondrocyte implantation. Clinical outcome as measured by the Knee injury and Osteoarthritis Outcome Score at 12 to 18 months after characterized chondrocyte implantation was comparable with microfracture at this stage. Both treatment groups had a similar mean baseline overall Knee injury and Osteoarthritis Outcome Score (56.30 +/- 13.61 and 59.53 +/- 14.95 for microfracture and characterized chondrocyte implantation, respectively), which increased in both groups to 70.56 +/- 12.39 and 72.63 +/- 15.55 at 6 months, 73.26 +/- 14.66 and 73.10 +/- 16.01 at 12 months, and 74.73 +/- 17.01 and 75.04 +/- 14.50 at 18 months, respectively. Both techniques were generally well tolerated; the incidence of adverse events after characterized chondrocyte implantation was not markedly increased compared with that for microfracture. CONCLUSION: One year after treatment, characterized chondrocyte implantation was associated with a tissue regenerate that was superior to that after microfracture. Short-term clinical outcome was similar for both treatments. The superior structural outcome may result in improved long-term clinical benefit with characterized chondrocyte implantation. Long-term follow-up is needed to confirm these findings.

In vitro measurement of patellar kinematics following reconstruction of the medial patellofemoral ligament.

This study compares the effects of two different techniques of medial patellofemoral ligament (MPFL) reconstruction, and proximal soft tissue realignment on patellar stabilization against lateral dislocation. Eight human cadaver knee specimens with no radiological pathomorpholgy on a straight lateral view, contributing to patellofemoral instability, were mounted in a kinematic knee simulator and isokinetic extension was simulated. Patellar kinematics were measured with an ultrasound positioning system (zebris) while a 100 N laterally directed force was applied to the patella. The kinematics were compared with intact knee conditions under MPFL deficient conditions, as well as following dynamic reconstruction of the MPFL using a distal transfer of the semitendinosus tendon, following static reconstruction by a semitendinosus autograft, and following proximal soft tissue realignment of the patella (Insall procedure). Dynamic reconstruction of the MPFL resulted in no significant alteration (P = 0.16) of patellar kinematics. Static reconstruction of the MPFL significantly medialized (P < 0.01) the patellar movement without, but restored intact knee kinematics under the laterally directed force. In contrast, following proximal soft tissue realignment, the patellar movement was constantly medialized and internally tilted (P = 0.04). Dynamic and static reconstruction of the MPFL create sufficient stabilization of the patella. Following proximal soft tissue realignment, the patellar position was over-medialized relative to intact knee conditions, which could lead to an overuse of the medial retropatellar cartilage.

Shoulder arthrodesis: indications, technique, results, and complications.

Complications after shoulder arthrodesis are frequent. Through results and comparisons with the literature, the presented article analyzes the correlation of complications with the specific operative techniques, indications, and postoperative treatment. Between 1964 and 2001, a total of 43 cases of shoulder arthrodesis (13 screw and 30 plate arthrodeses) were performed and then analyzed after a mean of 6.7 years (range, 0.5-36 years). Surgery was carried out on 10 female patients (23%) and 33 male patients (77%) with a mean age of 35 years (range, 11-82 years). These patients had the following indications: paralysis (32 [74%]), osteoarthritis or humeral head necrosis (15 [35%]), infection (7 [16%]), and persistent shoulder instability (6 [14%]). The extent of active movement after arthrodesis was 56 degrees abduction (range, 20 degrees - 90 degrees) and 60 degrees forward flexion (range, 20 degrees - 105 degrees), with an increase in the Constant score in all cases, from a mean of 27 points preoperatively to 57 points postoperatively (difference, 30 points). The patients rated the outcome of surgery as excellent, good, or satisfactory in 91% of cases. Complications after shoulder arthrodesis were noted in 12 of 43 patients (28%). The most frequent complications after screw/plate arthrodesis included pseudarthrosis, 2 (15%)/3 (10%); infection, 1 (8%)/4 (13%); and fracture of the humerus, 0/4 (13%). No specific judgment can be attributed to the different osteosynthesis techniques used in shoulder arthrodesis, either in the cases presented at our clinic or in the literature. Pseudarthrosis appeared to be less frequent in cases of plate arthrodesis compared with screw arthrodesis. However, the application of plates resulted more often in infection, postoperative fractures of the humerus, and the necessity for removal of material. Particularly in patients with paralysis, a shoulder arthrodesis resulted in an improvement in postoperative active function and presented a suitable operative option.

Primary stability of shoulder arthrodesis using cannulated cancellous screws.

There are no biomechanical studies available concerned with the primary stability of shoulder arthrodesis. The aim of our biomechanical investigations was to ascertain a minimal material combination with high primary stability for shoulder arthrodesis. For that purpose, the primary stability of 6 different forms of screw arthrodesis was investigated under the stress of abduction, adduction, anteversion, and retroversion. The mean values of the screw arthrodeses were compared with those of a 16-hole plate arthrodesis. All tests were carried out on 24 human specimens without destruction by use of a materials testing machine. The most stable form of screw arthrodesis for the load directions of abduction, adduction, anteversion, and retroversion results from a specific configuration of screws comprising 3 horizontal humeroglenoid screws and 3 vertical acromiohumeral screws (318.5 +/- 99.0 N). For three forms of arthrodesis, each with 3 humerus-glenoid screws (299.9 +/- 95.4 N), no significant difference (P = .530) was found compared with a 16-hole plate arthrodesis (293.4 +/- 89.3 N). The plate arthrodeses only achieved higher power values on abduction and adduction stress in comparison with screw arthrodesis with 3 humerus-glenoid screws. The difference was insignificant. Because arthrodesis with 3 humerus-glenoid screws was significantly more stable on stress of anteversion and retroversion, this particular screw arthrodesis is considered superior to plate arthrodeses. The use of the most stable form of screw arthrodesis may reduce nonunion.

Infrapatellar fat pad pressure and volume changes of the anterior compartment during knee motion: possible clinical consequences to the anterior knee pain syndrome.

This biomechanical study was performed to measure tissue pressure in the infrapatellar fat pad and the volume changes of the anterior knee compartment during knee flexion-extension motion. Knee motion from 120 degrees of flexion to full extension was simulated on ten fresh frozen human knee specimens (six from males, four from females, average age 44 years) using a hydraulic kinematic simulator (30, 40, and 50 Nm extension moment). Infrapatellar tissue pressure was measured using a closed cell sensor. Infrapatellar volume change in the anterior knee compartment was evaluated subsequent to removal of the fat pad using a water-filled bladder. We found a significant increase of the infrapatellar tissue pressure during knee flexion, at flexion angles of <20 degrees and >100 degrees . The average tissue pressure ranged from 343 (+/-223) mbar at 0 degrees to 60 (+/-64) mbar at 60 degrees of flexion. The smallest volume in the anterior knee compartment was measured at full extension and 120 degrees of flexion, whereas the maximum volume was observed at 50 degrees of flexion. In conclusion, the data suggest a biomechanical function of the infrapatellar fat pad at flexion angles of <20 degrees and >100 degrees , which suggests a role of the infrapatellar fat pad in stabilizing the patella in the extremes of knee motion.