Patellofemoral kinematics in mobile-bearing and fixed-bearing posterior stabilised total knee replacements: a cadaveric study.

PURPOSE: The aim was to compare the patellar kinematics in the normal knee, fixed-bearing (FB) and mobile-bearing total knee replacement (MB-TKR). The hypothesis that a mobile-bearing TKR has a more natural patellar movement was tested. METHODS: Computer navigation was used to track the patella in nine whole lower extremities in the natural knee and in the same knee with a posterior stabilised FB-TKR and a posterior stabilised MB-TKR from 0° to 90° flexion. The form and position of the trochlea in the natural knee and the patellar groove of the TKR femoral component was also analysed. RESULTS: There were no differences between the FB and MB-TKRs. But the patella in the TKRs at flexion angles of more than 50° had a more medial tilt compared to the natural knee. The patella of the natural knee tended to rotate externally with flexion, this was not seen in both TKR types. There were no significant differences in absolute mediolateral translation nor in translation relative to the patellar groove. During flexion, the patella lost contact with its groove earlier in the TKRs. The radius of the patellar groove of the femoral component was larger. The groove extended more superiorly and less far posteriorly, it was also positioned further laterally compared to the natural knee. CONCLUSIONS: There are subtle kinematic differences in patellar tracking between the natural knee and a TKR presumably due to differences in the shape and position of the patellar groove. There are no kinematic differences in patellar movement between the FB- and MB-TKR.

The surgical anatomy of the blood supply to the femoral head: description of the anastomosis between the medial femoral circumflex and inferior gluteal arteries at the hip.

The inferior gluteal artery is described in standard anatomy textbooks as contributing to the blood supply of the hip through an anastomosis with the medial femoral circumflex artery. The site(s) of the anastomosis has not been described previously. We undertook an injection study to define the anastomotic connections between these two arteries and to determine whether the inferior gluteal artery could supply the lateral epiphyseal arteries alone. From eight fresh-frozen cadaver pelvic specimens we were able to inject the vessels in 14 hips with latex moulding compound through either the medial femoral circumflex artery or the inferior gluteal artery. Injected vessels around the hip were then carefully exposed and documented photographically. In seven of the eight specimens a clear anastomosis was shown between the two arteries adjacent to the tendon of obturator externus. The terminal vessel arising from this anastomosis was noted to pass directly beneath the posterior capsule of the hip before ascending the superior aspect of the femoral neck and terminating in the lateral epiphyseal vessels. At no point was the terminal vessel found between the capsule and the conjoined tendon. The medial femoral circumflex artery receives a direct supply from the inferior gluteal artery immediately before passing beneath the capsule of the hip. Detailed knowledge of this anatomy may help to explain the development of avascular necrosis after hip trauma, as well as to allow additional safe surgical exposure of the femoral neck and head.

Focal cortical dysplasia: long term seizure outcome after surgical treatment.

BACKGROUND: Studies of long term outcome after epilepsy surgery for cortical malformations are rare. In this study, we report our experience with surgical treatment and year to year long term outcome for a subgroup of patients with focal cortical dysplasia (FCD). METHODS: We retrospectively analysed the records of 49 patients (females n = 26; males n = 23; mean age 25 (11) years) with a mean duration of epilepsy of 18 years (range 1-45). Preoperative MRI, histological results based on the Palmini classification and clinical year to year follow-up according to the International League Against Epilepsy (ILAE) classification were available in all patients. RESULTS: 98% of patients had a lesion on preoperative MRI. In addition to lobectomy (n = 9) or lesionectomy (n = 40), 14 patients had multiple subpial transections of the eloquent cortex. The resected tissue was classified as FCD type II b in 41 cases with an extratemporal (88%) and FCD type II a in 8 cases with a temporal localisation (100%). After a mean follow-up of 8.1 (4.5) years, 37 patients (76%) were seizure free, a subgroup of 23 patients (47%) had been completely seizure free since surgery (ILAE class 1a) and 4 patients (8%) had only auras (ILAE class 2). Over a 10 year follow-up, the proportion of satisfactory outcomes decreased, mainly within the first 3 years. During long term follow-up, 48% stopped antiepileptic drug treatment, 34% received a driver's license and 57% found a job or training. CONCLUSION: Surgical treatment of epilepsy with FCD is not only successful in the short term but also has a satisfying long term outcome which remains constant after 3 years of follow-up but is not associated with better employment status or improvement in daily living.

Development of the popliteomeniscal fasciculi in the fetal human knee joint.

PURPOSE: The purpose of this study is to better understand the function of the popliteomeniscal fasciculi and their relationship to the popliteus tendon and the lateral meniscus by describing these structures during embryonic development. TYPE OF STUDY: Anatomic dissection and histologic evaluation. METHODS: Twelve fresh-frozen lower extremity specimens (6 paired limbs) from second and third trimester human fetuses were obtained from spontaneous abortions. Each specimen was fixed in formalin and decalcified in 9.0% nitric oxide. The specimens were prepared by removal of all skin and most of the soft tissues before dissection of the lateral meniscus, parts of the posterolateral joint capsule, and the popliteus tendon and muscle. The right-side specimens were sectioned in the transverse plane, and the left-side specimens in the coronal plane. Histologic sections were prepared with H&E and Masson's trichrome stains. Light microscopy was used to evaluate the lateral meniscal attachment, with detailed attention to the popliteomeniscal fasciculi. RESULTS: The close interrelationship of lateral meniscus and popliteus tendon, especially during embryologic development, does give a better understanding how the fasciculi stabilize the lateral meniscus and allow the popliteus tendon to function as a retractor of the lateral meniscus. The fasciculi consist of 3 layers including a dense collagen layer, a vascular layer, and a synovial or capsular layer. CONCLUSIONS: During embryologic development, the fasciculi appeared to provide a vascular supply to the lateral meniscus adjacent to the popliteal hiatus where the meniscus is devoid of capsular attachments.

The skeletally fixed knee hinge for the grossly unstable knee.

This study examined whether a skeletally fixed prefabricated knee hinge can provide the intact or unstable knee with normal motion through a specific arc of motion. Eight cadaveric knee specimens were used. The amount of motion mismatch between knee and hinge motion was evaluated at six different knee flexion angles. With all knee ligaments intact, addition of the hinge resulted in increasing amounts of joint compression with knee flexion. When all knee ligaments were cut, there was some degree of distraction with 0 degrees of knee flexion, which seemed to gradually decrease and become compressive at 80 degrees of flexion. These values were not statistically significant. In contrast, the mismatch between anterior and posterior tibial translation mismatch was statistically significant. With the ligaments intact, the addition of the hinge resulted in increased amounts of posterior tibial translation, which became significant at 80 degrees of flexion. Similarly, when the ligaments were cut with the hinge intact, there was an increasing amount of posterior tibial translation, which became significant at 60 degrees of flexion. There was also a significant amount of anterior tibial translation at 0 degrees in this group. These results indicate that the hinge allows only a limited range of motion that does not significantly alter tibial translation or joint compression or distraction. Whether this amount of motion is enough to improve the outcome of the grossly unstable knee is unknown. The use of a more sophisticated hinge system might accomplish a greater range of anatomic motion before significant mismatch occurs between hinge and knee motion.

Contact pressures at osteochondral donor sites in the knee.

The purposes of this study were to determine whether any of the commonly recommended osteochondral donor sites are nonarticulating throughout a functional range of knee motion, and to determine the differential contact pressures for these sites. Ten commonly recommended sites for osteochondral harvest were evaluated with pressure-sensitive film through a functional range of motion with a model that simulated nonweightbearing resistive extension of the knee. All 10 donor sites demonstrated a significant contact pressure through 0 degree to 110 degrees of knee motion. The different color density measurements between donor sites were also significant. Although donor sites 1, 2, 9, and 10 demonstrated significantly less contact pressure than the sites with the greatest contact pressure, the difference in mean pressures was small. No osteochondral donor site tested was free from contact pressure. It is currently unknown whether articular contact at these osteochondral donor sites will lead to degenerative changes or any other problems.

Interference screw position and hamstring graft location for anterior cruciate ligament reconstruction.

Anterior cruciate ligament reconstruction with hamstring tendon graft and interference screw fixation has recently been considered. Concerns for the use of interference screws with soft tissue grafts include damage to the graft during screw insertion, decreased fixation strength, and a decrease in the bone-tendon contact area for healing within the tunnel when the screw is placed in an eccentric position. This last concern could be addressed by placing the interference screw centrally between the four limbs of the hamstring graft. The purpose of this study was to determine the mode of failure, the pullout force, and graft slippage before graft fixation failure of hamstring tendons fixed with an interference screw positioned eccentrically in relation to the hamstring tendons verses an interference screw positioned centrally between the four graft limbs. The semitendinosus and gracilis tendons were harvested from six, fresh cadaveric specimens. Each tendon was divided into two segments of equal length. Both the semitendinosus and gracilis tendon segments were looped to form four strands. The specimens were then fixed with a bioabsorbable interference screw in the two different positions and pulled from a standardized polyurethane foam. All tendons in both groups failed by pulling out from between the interference screw and tunnel, regardless of the screw position. No tendon was cut by the screw in either group. There was no significant difference between the forces required to produce specific amounts of graft slippage between the two fixation techniques tested. There was no significant difference between the average total slippage at maximum pullout, 11.8 mm for the screw placed in the eccentric position and 13.7 mm for the screw placed in the central position. The maximum pullout force averaged 265.3 N for the screw placed in the eccentric position, and 244.7 N for the screw placed in the central position; these values were not significantly different. Placement of the interference screw in the central position did not compromise strength and it improves graft contact within the bone tunnel. Interference screw fixation, when applied against a bone plug, has been shown to consistently have a pullout force of more than 400 N.

Popliteomeniscal fasciculi and lateral meniscal stability.

In an attempt to understand better the contribution of the anteroinferior and posterosuperior popliteomeniscal fasciculi to lateral meniscus stability, we objectively evaluated the stability of the lateral meniscus before and after sequentially sectioning these fasciculi. In the biomechanical model, we attempted to account for the inherent limitations of arthroscopic evaluation of lateral meniscal stability. When the fasciculi were intact, the average lateral meniscal motion with a 10-N load was 3.6 mm. When the anteroinferior fascicle was disrupted, the average lateral meniscal motion with a 10-N load was 5.4 mm. The mean increase in motion from the intact state was 1.8 mm or 50%, which was significant. When both fasciculi were disrupted, the average lateral meniscal motion with 10-N load was 6.4 mm. The mean increase in motion from the intact state was 2.8 mm or 78% and from the single fascicle disruption state was 1.0 mm or 18%, both differences were significant. The meniscus did not become locked with any of these loading trials, and it spontaneously reduced to the original position when unloaded. Both fasciculi make significant contributions to meniscal stability. Even though the meniscus never became locked in the joint when loaded during this study, with the variable loads seen with normal activities mechanical symptoms might be expected when meniscal motion is almost double. An increase in lateral meniscal motion at the time of surgery may aid in the diagnosis of fasciculi disruption, despite normal meniscal structure on magnetic resonance images and at arthroscopic visualization.

Popliteomeniscal fasciculi and the unstable lateral meniscus: clinical correlation and magnetic resonance diagnosis.

We hypothesize that disruption of the fascicular attachments between the popliteus and lateral meniscus can result in gross instability of the meniscus producing locking of the knee. This study brings attention to the importance of the clinical examination, and the need for clinical correlation to magnetic resonance (MR) studies. We report on three patients referred with the history of mechanical locking episodes of their knee. Initial MR examinations were all read as normal before referral to our institution. On close review of these MR examinations, popliteomeniscal fascicular disruption could be seen in each case. Each of these patients had arthroscopic-repair of these meniscal detachments. At 1-year follow-up, all patients had resolution of mechanical symptoms. Each patient had confirmation of their repair with repeat arthroscopy or MR and arthrographic examinations. An anatomic specimen was used to identify the popliteus muscle and tendon, the lateral meniscus, the antero-inferior popliteomeniscal fascicle, and the postero-superior popliteomeniscal fascicle attachments. MR images of the same anatomic specimen show both superior and inferior fasciculus attachments to the capsule. MR examples of the intact and disrupted antero-inferior and postero-superior popliteomeniscal fasciculi have been correlated to anatomic specimens to help familiarize the orthopaedic surgeon with these important stabilizing structures.

[Hemoperfusion by means of encapsuled charcoal for the treatment of exogenous and endogenous intoxications]. / Hämoperfusion durch verkapselte Aktivkohle zur Therapie exogener und endogener Intoxikationen

The method developed by Chang for using in collodion and albumin encapsuled charcoal as artificial cells for hemoperfusion has been studied in vitro. The capacity for the absorption of more or less dialysable exogenous substances (barbiturate, Diazepam, Parathion) and an endogenous toxic metabolite (p-hydroxyphenyl acetic acid) has been examined. With the absorption unit one can eliminate 80 to 90 per cent of the initial concentration of barbiturate, Diazepam and p-hydroxyphenyl acetic acid in about 90 min, of Parathion about 50 per cent in the same time, whereas bromide and ammonia are not absorbed. Attempts to avoid regional heparinisation by the incorporation of heparin into the capsule of charcoal granules were not successful. Assuming correct preparation of the hemoperfusion system, observance of steril precoutions and regional heparinisation, the use of the "detoxication shunt" is a promising means in the treatment of severe exogenous and endogenous intoxications which are not accessible by conventional therapeutic means.