All-Inside Lateral Meniscal Repair via Anterolateral Portal Increases Risk of Vascular Injury: A Cadaveric Study

PURPOSE

To compare the distance from the device tip to the neurovascular structures during an all-inside medial and lateral meniscal repair using anteromedial and anterolateral portals in a fresh-frozen cadaveric study.

METHODS

Ten fresh-frozen cadaveric knees were studied. The popliteal artery, popliteal vein, and tibial nerve were identified after dissection via a posterior approach. An all-inside meniscal repair device was set to a 20-mm depth limit and inserted into a fixed point in the posterior horn at the meniscocapsular junction. This was performed for medial and lateral menisci via anteromedial and anterolateral arthroscopic portals. The distances between the device tip and the neurovascular structures were measured. We performed t tests to determine statistical significance.

RESULTS

The distance between the device and popliteal artery was significantly closer when aimed at the posterior horn of the lateral meniscus via the anterolateral portal (4.7 ± 2.3 mm) versus the anteromedial portal (13.0 ± 8.0 mm, P = .010). The distance to the popliteal vein was closer via the anterolateral portal (6.7 ± 2.9 mm) versus the anteromedial portal (13.9 ± 5.8 mm, P = .004). For medial meniscal repair, the distance to the popliteal artery was significantly closer via the anteromedial portal (12.8 ± 11.3 mm) versus the anterolateral portal (23.8 ± 7.7 mm, P = .022). The distance to the popliteal vein was closer via the anteromedial portal (16.5 ± 11.3 mm) versus the anterolateral portal (28.3 ± 8.2 mm, P = .017). No significant difference was found in the distance to the tibial nerve when aimed at either meniscus via either portal.

CONCLUSION

For all-inside meniscal repair, the popliteal vein is at risk and the popliteal artery is at high risk of injury when the posterior horn of the lateral meniscus is repaired via an anterolateral working portal.

CLINICAL RELEVANCE

The popliteal artery and vein are at risk of injury when the posterior horn of the lateral meniscus undergoes all-inside repair via the anterolateral portal. Surgeons need to be aware of the risks when performing this repair.

Rudiment resorption as a response to starvation during larval development in the sea urchin Strongylocentrotus droebachiensis

Phenotypic flexibility (reversible phenotypic change) enables organisms to couple internal, ontogenetic responses with external, environmental cues. Phenotypic flexibility also provides organisms with the capacity to buffer stereotypical internal, developmental processes from unpredictable external, ecological events. Echinoids exhibit dramatic phenotypic flexibility in response to variation in exogenous nutrient supplies. The extent to which echinoids display this flexibility has been explored incompletely and research hitherto has been conducted predominantly on larval structures and morphologies. We investigated experimentally the extent to which the primordial juvenile, the developing rudiment, can exhibit the first phase in phenotypic flexibility among individuals. We report for the first time on rudiment regression and complete resorption as a response to starvation during larval development in the sea urchin Strongylocentrotus droebachiensis (O.F. Müller, 1776) and identify a developmental “window of opportunity” within which this can occur. Based on our observations and previous suggestions, we speculate that sea urchin rudiments might provide means of buffering development during unfavorable conditions.

Custom Mega Prosthesis in Metachronous Osteosarcoma

Background: The objective of the current study was to determine the incidence, clinical and pathologic characteristics, and outcome of patients with conventional osteosarcoma who developed metachronous tumours and treated by limb salvage surgery with Custom Mega Prosthesis.

Methods: Among 1198 osteosarcoma patients who were treated with limb salvage surgery and implantation of custom mega prosthesis, 6 patients were found to have metachronous lesions. The absence of pulmonary metastases was confirmed by chest radiographs and computed tomography while radionuclide bone scan and biopsy were used to confirm the absence of skeletal metastases. The patients were treated by limb salvage surgery with custom mega prosthesis for the metachronous tumour and functional outcome was evaluated by MSTS scores.

Results: Index primary tumours involved the femur (n=3) and the tibia (n=3) and were treated with limb salvage surgery using endoprosthetic reconstruction. Single metachronous tumours developed in the all of these patients with the interval between identification of the primary tumour to development of the metachronous tumours varying from 18 months to 41 months. All metachronous tumours were treated with neoadjuvant chemotherapy and limb salvage surgery. We obtained excellent functional outcome for primary tumours and good functional outcome for metachronous tumours. Two patients succumbed to disease due to pulmonary and cerebral metastasis during follow-up.

Conclusions: With advances in survival rate in the multidrug chemotherapy era in the post tumoursresection period, advanced diagnostic modalities help in diagnosing metachronous osteosarcoma. It should be recognized as important sequelae in long-term survivors. Meticulous follow-up is required to permit early detection and successful therapeutic intervention. Limb salvage surgery has provided consistent good results in metachronous osteosarcoma patients.

Shifts in striatal responsivity evoked by chronic stimulation of dopamine and glutamate systems

Dopamine and glutamate are key neurotransmitters in cortico-basal ganglia loops affecting motor and cognitive function. To examine functional convergence of dopamine and glutamate neurotransmitter systems in the basal ganglia, we evaluated the long-term effects of chronic stimulation of each of these systems on striatal responses to stimulation of the other. First we exposed rats to chronic intermittent cocaine and used early-gene assays to test the responsivity of the striatum to subsequent acute motor cortex stimulation by application of the GABA(A) (gamma-aminobutyric acid alpha subunit) receptor antagonist, picrotoxin. Reciprocally, we studied the effects of chronic intermittent motor cortex stimulation on the capacity for subsequent acute dopaminergic treatments to induce early-gene activation in the striatum. Prior treatment with chronic intermittent cocaine induced motor sensitization and significantly potentiated the striatal expression of Fos-family early genes in response to stimulation of the motor cortex. Contrary to this, chronic intermittent stimulation of the motor cortex down-regulated cocaine-induced gene expression in the striatum, but enhanced striatal gene expression induced by a full D1 receptor agonist (SKF 81297) and did not change the early-gene response elicited by a D2 receptor antagonist (haloperidol). These findings suggests that repeated dopaminergic stimulation produces long-term enhancement of corticostriatal signalling from the motor cortex, amplifying cortically evoked modulation of the basal ganglia. By contrast, persistent stimulation of the motor cortex inhibits cocaine-stimulated signalling in the striatum, but not signalling mediated by individual dopamine receptor sites, suggesting that chronic cortical hyperexcitability produces long-term impairment of dopaminergic activity and compensation at the receptor level. These findings prompt a model of the basal ganglia function as being regulated by opposing homeostatic dopamine-glutamate neurotransmitter interactions. The model provides a framework for analysing the neurological alterations associated with disorders of the basal ganglia and their treatment with pharmacotherapies affecting dopamine and glutamate neurotransmitter systems.